Content
Abstract 1
1 Characteristics of the mill 2500 4
1.1 Composition and technical characteristics of equipment 4
1.2 Technical characteristics of the equipment of the mill 6
2 TECHNOLOGICAL PROCESS 7
2.1 Brief description of the main and auxiliary equipment of the 2500 hot rolling mill 7
2.2 Technological process of the mill 2500 10
2.2.1 Mill assortment by steel grades and strip sizes 12
2.2.3 Start-up of the mill after repair or reloading of rolls 14
2.2.5 Calculation of compression modes 16
2.2.5.1 Development of reduction modes for finishing group 16
2.2.5.1.1 Crimp mode 16
2.2.5.1.2 Tension mode 19
2.2.5.2 Calculation of the thermal regime and the cooling regime on the discharge roller table 25
2.2.5.3 Calculation of mill productivity 27
2.3 Adjustment and installation of technological parameters when rolling metal on mill 28
2.3.1 Rolling the tuning profile 28
2.3.2 Setting the normal rolling mill 28
2.3.3 Winding strips into rolls 31
2.4 Technical requirements for the supply of coils from the mill to the units and to the cold rolling shop 33
2.5 Quality control of strips and their possible defects 33
3. Reconstruction of the roughing group of stands. 34
3.1 Goals of modernization of the mill. 34
3.2 Reconstruction of the roughing group of stands. 35
3.2.1. Technical characteristics of the universal roughing stand. 37
3.3 Calculated part 40
3.3.1 Temperature conditions for rolling slabs 40
3.3.2. Calculation of work and backup rolls 42
4 SAFETY AND ENVIRONMENTAL 49
4.1 Analysis of hazardous and harmful production factors. 49
4.2 Measures to ensure occupational safety 52
4.3 Environmental protection 58
4.4 Prevention and elimination of emergencies in LPC No. 4 61
5 ANALYSIS OF TECHNICAL AND ECONOMIC INDICATORS 65
5.1 Organizational and legal form of the enterprise 65
5.2 Marketing research of the product sales market 67
5.3 Financial Evaluation of the Project 69
5.3.1 Calculation of the production program. 69
5.4 Calculating Capital Cost Estimates 73
5.5 Organization of labor and wages at site 75
5.6 Calculation of the change in the cost of production under the influence of 80
events 80
5.7 Calculation of the main technical and economic indicators of the project 83
5.7.1 Calculation of net profit 83
CONCLUSION 86
LIST OF USED SOURCES 87
1 Characteristics of the mill 2500
1.1 Composition and technical characteristics of equipment
- reversible duo stand;
- widening cage quarto;
- universal quarto stand.
Slab pusher is designed to feed slabs from a lifting table to a roller conveyor. Pushing is carried out by rack and pinion rods, connected by a pushing traverse. The roller table in front of the furnaces is located on the front side of the heating furnaces and is designed to feed slabs to the furnaces. If necessary, slabs can be fed to the furnaces via a roller table directly from the slab harvesting devices. The roller table in front of the furnaces consists of 19 sections of the same type with a group drive.
- reversible duo stand;
- widening cage quarto;
- reversible quarto stand;
- finishing crusher - duo stand;
- 7 finishing stands for quarto.
1.2 Technical characteristics of the mill equipment
The stands of the closed stands with I-beams are made of cast steel. Work rolls - steel and cast iron. Back-up rolls are forged steel. Work roll bearings: double row with tapered rollers, back-up roll bearings - fluid friction. Pressure mechanism - with globoid gearboxes for each screw. The mechanism for balancing the upper backup roll is hydraulic with an upper cylinder arrangement. A bronze nut of a pressure screw is pressed into the upper cross member of each bed. Grease is supplied to the thread of the pressure screw through the holes in the nut. For the convenience of roll transfer, the width of the frame windows on the transfer side is 10 mm larger than on the drive side.
2 TECHNOLOGICAL PROCESS
Technical re-equipment of hot rolling shops is caused by the growing demand for this economical type of rolled products. The main directions of production growth are the construction of new hot rolling mills and the reconstruction of existing shops. As the feasibility study shows, reconstruction is a more economical, socially feasible and environmentally friendly method, and can satisfy more than half of the planned production growth.
2.1 Brief description of the main and auxiliary equipment of the 2500 hot rolling mill
Composition and technical characteristics of equipment
The 2500 hot strip mill consists of a charging section, a heating furnace section, a roughing and finishing group with an intermediate roller table between them and a coiling line. The loading area consists of a slab storage and a loading roller table, 3 lifting tables with pushers.
The section of the heating furnaces consists of actually 6 heating methodical furnaces, a roller table in front of the furnaces with pushers and a sub-furnace roller table after the furnaces.
The roughing group consists of stands:
- reversible duo stand;
- widening cage quarto;
- reversible universal quarto stand;
- universal quarto stand.
Intermediate roller conveyor provides dumping and cutting of underruns.
The finishing group includes flying shears, a finishing grinder (duo stand), 7 quarto stands. Between stands 6, 7 and 8, devices for accelerated strip cooling (inter-stand cooling) are installed.
The coiling line includes a discharge roller conveyor with 30 strip cooling sections (top and bottom spray). Four coilers with roll tilters.
The mill consists of the following sections: a section of heating furnaces and the actual mill with coilers.
The section of heating furnaces includes: lifting tables; slab pusher; roller conveyor in front of the ovens; double pusher; feed roller conveyor; oven buffers; heating furnaces.
Lift tables are installed at the loading roller tables in front of the furnaces, they are used to receive slabs and to feed them one by one to the roller conveyor using a pusher.
Slab pusher is designed to feed slabs from a lifting table to a roller conveyor. Pushing is carried out by rack and pinion rods connected by a pushing traverse. The rods are moved by right and left mechanisms with a common drive.
The roller table in front of the furnaces is located on the front side of the heating furnaces and is designed to feed slabs to the furnaces. If necessary, slabs can be fed to the furnaces via a roller table directly from the slab harvesting devices. The roller conveyor in front of the furnaces consists of 19 sections of the same type with a group drive.
The double pusher is used to feed the slabs of the loading roller table into the double-row heating furnace and move them through the furnace until they are dispensed onto the receiving roller table.
The feed roller conveyor is designed to receive slabs falling out of the furnace and transport them to the working stands of the mill.
The buffers at the kiln are designed to extinguish the impact energy of the slabs pushed along the inclined beams from the kiln. Buffers consist of a plate, bed, springs. The buffers have 4 cars each, on which coil springs are located to absorb the slab impact. Buffer plates with inclined front plane for better absorption of impact energy.
Heating furnaces are designed to heat up slabs before rolling.
Methodical furnaces are equipped with recording devices and automatic regulators, i.e. automatic control devices.
Methodical furnaces operate on evaporative cooling with forced circulation. It is possible to switch the unit from evaporative cooling to service water.
The rolling span includes a roughing and finishing group of stands.
The draft group includes:
- reversible duo stand;
- widening cage quarto;
- reversible quarto stand;
- 1 universal quarto stand - No. 3.
The finishing group includes:
- finishing descaler;
- duo stand;
- 7 finishing stands for quarto.
In front of the finishing scaler, 35 mm flying shears are installed to trim the front and rear ends of the roll.
Technical characteristics of the mill equipment.
The stands of the closed stands with I-beams are made of cast steel. Work rolls - steel and cast iron. Back-up rolls are forged steel. Bearings of work rolls are roller: double row with tapered rollers, bearings of back-up rolls with liquid friction. Pressure mechanism with globoid gearboxes for each screw. The mechanism for balancing the upper backup roll is hydraulic with an upper cylinder. A bronze nut of a pressure screw is pressed into the upper cross member of each bed. Grease is supplied to the thread of the pressure screw through the holes in the nut. For the convenience of roll transfer, the width of the frame windows on the transfer side is 10 mm larger than on the drive side.
The work roll chocks and the corresponding back-up roll chocks are lined with replaceable strips. For a stable position of the work rolls during rolling, their axes are located at a distance of 10 mm along the metal path relative to the axis of the backup rolls.
The work roll chocks are attached to the back-up roll chocks with latches on the transfer side. On the drive side, the chocks of the work rolls are fixed, which allows axial displacement of the chocks as the rolls lengthen from thermal expansion. Back-up rolls are fixed in the stand against axial movement by fixing the chocks from the transshipment side to the beds of the kerchiefs. On the drive side, the back-up roll chocks are also not fixed. The electric motors of the pressing device of the roughing group stands and the scale breakers are interconnected by a fractional decoupling clutch and an electromagnetic uncoupling drive. This clutch allows the joint and separation of the actuator motors of the push mechanism. On the pressing devices of the finishing stands, the electromagnetic clutches of the screws are provided by the electrical synchronization circuit.
The drive power of the pressure mechanism is sufficient to tighten the screws during rolling while passing the metal in the rolls.
2.2 Technological process of the mill 2500
KKTs slabs (cast billet) and hot-rolled OTs slabs are used as the initial billet for the 2500 mill.
Cast billet KKTs:
- the chemical composition of the steel must meet the requirements of the relevant GOST or TU;
- cast slabs must be cast in accordance with STO MMK 98-2000 and cut to lengths in accordance with UP orders;
- the dimensions of the slabs and the maximum deviations must comply with the requirements of Table 2.1.
- the convexity (concavity) of the edges should not exceed 10 mm per side;
- rhombicity (diagonal difference) of the slab cross-section should not exceed 10 mm;
- the slant of the cut should not exceed 30 mm;
- the crescent shape (curvature across the width) of the slabs should not be more than 10 mm by
1 m in length, non-flatness should not be more than 60 mm for the length of the workpiece;
- on the surface of slabs there should be no belts, sagging, captivity, cracks, bubbles, slag inclusions;
Table 2.1- Slab dimensions and limit deviations
Name Size range, mm Limit deviations, mm
Thickness 250 +10; -5
Width 1000-2350 ± 1%
Length 2700-5550 + 60
- traces of the reciprocating movement of the crystallizer and snakes (splashes) without accompanying cracks are not a rejection sign;
- on the ends of the blanks during visual inspection there should be no cracks, traces of axial discontinuity, burrs;
- slabs must be clearly marked with the following content: the number of the heat, strand and the serial number of the slab. Sometimes there is a duplicate marking of the melt number on the ends of the slabs;
- slabs are handed over and accepted by theoretical weight. The theoretical mass is calculated using the formula:
Ma = Lsl? Msl; (2.1)
where Msl is the mass of the slab, t; Lsl - slab length, m;
M1m = h * b * 7820 - mass of 1 m of the length of the workpiece, where h is the thickness of the workpiece, m; b - workpiece width, m; 7820 - density of the cast slab, kg / m3.
Hot-rolled rectangular billet from carbon, low-alloy and alloy steels:
- dimensions and maximum deviations must correspond to those indicated in table 2.2. according to OST 14-16-17-90:
- the slab cut should be no more than 30 mm;
- the crescent shape of the slabs should not be more than 10 mm per 1 m of length, the deviation from flatness should not be more than 20 mm per 1 m;
- the shape of the slab must be rectangular. The width of the flat section on the lateral edges of the slabs must be at least 40% of the slab thickness. The convexity (concavity) of the side faces should not exceed 10 mm per side;
- the chemical composition of the slabs must comply with the ND;
- the ends of the slabs, corresponding to the head and bottom parts of the ingot, must be cut to the complete removal of shrinkage cavities, looseness and delamination;
- on the narrow edge of the slab, the heat number, steel grade and geometric dimensions of the slab are applied with paint.
Table 2.2 - Dimensions and limit deviations of slab billets
Name Dimensions, mm Interval of intermediate sizes, mm Limit deviations, mm
Thickness 80 to 150 150 to 350 5 10 ± 4 ± 5
Width From 750 to 2000 Over 2000 to 2200 50 50 ± 10 ± 12
Length From 2700 to 5550 100 +50; -thirty
Limit strip sizes:
thickness 1.8-10.0 mm,
width 1000-2350 mm,
coil weight up to 25 tons.
2.2.1 Mill assortment by steel grades and strip sizes
Broad-strip mill 2500 is designed for hot rolling of strips of the following steel grades:
- carbon steel of ordinary quality in accordance with GOST 16523-89, 14637-89, 380-71 and current TU;
- steel welded for shipbuilding in accordance with GOST 5521-86;
- high-quality and structural carbon steel in accordance with GOST 1577-81, 4041-71, 16523-89, 9045-93 and current TU;
- alloy steel grade 65G in accordance with GOST 14959-70;
- low-alloy steel in accordance with GOST 19281-89;
- steel 7ХНМ according to TU 14-1-387-84;
- carbon steel and low-alloy steel export performance according to TP,
STP based on foreign standards.
Limiting dimensions of strips: thickness 1.8-10.0 mm, width 1000-2350 mm, coil weight up to 25 tons.
2.2.2 Preparing and adjusting the mill after repair or roll transfer
Setting up a mill consists of the following sequential operations:
-setting the rolling level;
-alignment of rolls in the vertical plane - setting to parallelism;
-setting gaps between horizontal and vertical rolls and setting to "zero";
-installation and check of the wiring fittings and the guides of the stands.
Setting the rolling level. On the roughing group, the normal excess of the level of the lower working roll over the level of the roller table should be:
- for reversible cage "duo" - up to 40 mm;
- for an extension stand - up to 40 mm;
- for stand No. 3 - up to 30 mm.
In the finishing group, the excess of the level of the working roll above the level of the roller table should not exceed 25 mm.
The rolling level is maintained by installing spacers under the chocks of the lower backup rolls. The thickness of the spacers is determined by half the difference between the diameters of the old and new lower backup rolls according to the formula:
T = (Det - Dnov) / 2, (2.2)
where T is the thickness of the gaskets, mm;
Det - diameter of the old lower back-up roll, mm;
Bottoms - diameter of the new lower back-up roll, mm.
During reloading, before the backup rolls are worn out, several work rolls are reloaded. The difference between the diameters of the dumped and dumped work rolls is allowed for roughing stands up to 25 mm, finishing stands up to 20 mm.
If the difference is greater, the rolling level must be adjusted accordingly by installing shims.
Setting the gaps between horizontal and vertical rolls:
The setting of the finishing stands is carried out by the production foreman (senior roller of the finishing group).
The adjustment is carried out in a certain sequence according to the points of the instructions and is adjusted depending on the brand of rolled steels and other parameters (temperature regime).
Installation of wiring fittings. Output wiring should fit snugly to the work rolls, not have a gap and distortions. The lower guide is installed 30-50 mm below the upper generatrix of the lower work roll. The gap between the guide rails must exceed the width (strip). For finishing stands - 70 and 90 mm, respectively, for strips up to 1500 and more than 1500 mm wide.
2.2.3 Start-up of the mill after repair or roll transfer
Before the direct start-up of the mill, the electrical circuits of the mill are assembled. Then comes the check:
- areas of pressure screws; rolling lines;
- the correctness of the filling of the rolls, their fastening, the readiness of the rolls themselves;
-Correct installation of wiring and fastening of wiring knives and attachments;
- adjustment of the rulers in front of the stands to the appropriate width;
-installation and fastening of rolls cooling collectors; the position of the nozzles in the manifold and the direction of the water jet;
- the presence of grease and its state in the system; cooling systems for bearings and other rotating mechanisms;
- the position and state of the switches for balancing the back-up and work rolls of the stands.
- Commissioning of the mill after transshipment or idle time is made by bets in compliance with the following conditions:
-Rotation of the work rolls of the stands should be carried out at the lowest possible speed in order to avoid local heating of the rolls from friction by wires to the supply of cooling water;
-Rotation of the working rolls of the finishing stands at full speed with supplied wires without water supply is allowed no more than 5 minutes, after this time it is necessary to supply water to the rolls or reduce the rolls speed to the minimum.
2.2.4 The order of technological operations during rolling
The heated slabs are discharged from the furnace and fed to the “duo” stand through a discharge roller table. After rolling in the "duo" stand, the rolled stock is fed into the widening stand and transported along the roller table for rolling in roughing stands 2, 3. Rolling in the "duo" stand and stand 2 can be carried out by reverse. Rolling from roughing stands goes to l ........
LIST OF USED SOURCES
1 Korolev A.A. Design and calculation of machines and mechanisms of rolling mills: Textbook for universities. - M .: Metallurgy, 1985.
2 Konovalov Yu.V. Directory of the distributor. Reference edition in 2 books. Book 1. Production of hot-rolled sheets and strips. - M .: "Teplotekhnik", 2008.
3 Safyan M.M. Technology of production of broadband steel. - M .: Metallurgy, 1968.
4 Technological instruction TI 101-P-KhL3-45-2009. Developed by: P.P. Poletskov. - Magnitogorsk: OJSC MMK, 2009.
5 Grudev A.P. Rolling theory. Textbook for universities. - M .: Metallurgy, 1988.
6 Grudev A.P., Mashkin L.F., Khanin M.I. Rolling production technology - M .: Metallurgy, 1994
7 Marutov V.A., Pavlovsky S.A. Hydraulic cylinders. - M .: Mechanical Engineering, 1966.
8 Karataev E.D., Romashkevich L.F., Lyambakh R.V. and others // Steel. 1980. No. 2.
9 Mechanical equipment of wide-strip hot rolling mills / V.G. Makogon, G.G. Fomin, P.S. Grinchuk et al. - M .: Metallurgy, 1969.
10 Trishevsky I.S., Klepanda V.V., Litovchenko N.V. Setting up continuous hot rolling mills) - M .: Metallurgy, 1979.
11 Fomin G.G., Dubeykovsky A.V., Grinchuk P.S. Mechanization and Automation of Broadband Hot Rolling Mills, Moscow: Metallurgy, 1979.
12 Computer-controlled broadband automated mills / M.A. Benyakovsky, M.G. Ananevsky, Yu.V. Konovalov and others - M .: Metallurgy, 1984.
13 Nemtsev V.N. Economic analysis of the efficiency of an industrial enterprise. Tutorial. 2nd ed. MGTU Magnitogorsk, 2004.
14 Instruction on labor protection for the rolling mills of the hot rolling mill of Rolling Shop No. 4 IOT 3-8-01-2006. - Magnitogorsk: OJSC MMK, 2006.
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Introduction
One of the trends in the rolling industry is the expansion of temper rolling mills for finishing hot rolled steel. Hot-rolled thin strips, rolled on continuous broad-strip mills, are trained on mills installed in pickling lines or cut-to-length units. The tempering of hot-rolled metal, carried out with a nominal reduction of 1 - 1.5%, makes it possible to reduce the thickness variation, waviness and buckling of the strips, and to improve the quality of their surface.
Hot-rolled and cold-rolled annealed sheet steel intended for cold stamping and deep drawing is usually trained at temperatures below 80C about. During storage of sheet metal, deformation aging develops in it, which leads to intermittent deformation and the appearance of sliding lines and parts stamped from thin metal. To prevent this negative phenomenon, in some cases, tempering of cold-rolled steel intended for deep drawing is used. According to this method, to prevent aging, sheet steel is trained to 150 - 200 C about. Training in the specified temperature range is carried out during cooling, after annealing
The properties of steel treated by the heat tempering method remain practically unchanged if the temperature of the metal does not exceed the temperature of dynamic aging. The tensile diagram of specimens made of sheet steel, tempered at a temperature of 100 - 200 C o, has a monotonous "no tooth" and yield areas. By preventing aging of the metal and through warm tempering, calm steel can be replaced with boiling steel or semi-boiling steel.
The advantage of the heat tempering and rolling process of hot rolled mild steel sheets is that the cooling time of the coils in the warehouse after hot rolling is significantly reduced. In addition, the resistance of low-carbon steels at temperatures of warm tempering is much lower than 20-30 C o due to this, the energy-power parameters of the tempering processes and subsequent melting of strips are reduced. (1.c 12)
1. General part
1.1 Technological process in LPC - 4 OJSC MMK, a brief analysis of the main technological equipment
The launch date of Rolling Shop - 4 is December 27, 1960, on this very day the state commission signed an act of acceptance into operation of the 2500 hot rolling mill. The shop produces hot-rolled steel sheets with a thickness of 1.8-10.0 mm, width 1000-2350 mm, roll weight up to 25 tons as a commercial product. The mill produces 7 million tons of hot-rolled sheets per year.
Slabs are delivered to the shop in open cars from the oxygen-convection shop, which are then unloaded by bridge cranes equipped with magnetic grippers to the slab warehouse.
Slabs are fed to the furnaces via a transport and finishing line directly to the loading roller table near the furnaces, as well as using loading devices. Slabs are placed on trolleys by overhead cranes equipped with tongs. The maximum weight of a pile of slabs is 130 tons.
The stack of slabs is transported by crane to the lifting and lowering table, transferred to the table, and then the slabs are pushed one by one onto the loading roller table.
The slabs are transported by roller conveyors depending on the length, loaded into the furnace in one, in two rows and in a staggered manner. The position of the slabs relative to the axis of the furnace before they are sent to the furnace is determined by means of photosensors on the roller table near the furnace.
Slab heating temperature 1200-1250 ° depending on steel grade. When heated to the rolling temperature, the slabs are discharged from the furnaces one by one and placed smoothly without impact on the receiving roller table using the slab receiver.
Further, the slabs discharged from the furnace are transported by a receiving roller conveyor to the roughing mill, where the slab scale is removed, and then transported by a roller conveyor to the roughing group of stands. In the roughing group, the slab is rolled successively in a widening stand and in three universal stands. Descaling in the roughing group is provided with high pressure water using water descaling units. Depending on the section of the rolled strips, the thickness of the rolled stock after the roughing group is 26-50 mm.
After rolling in the roughing group, the rolling stock is transported by an intermediate roller table to the finishing group of stands. The final rolling of the strips to the specified thickness is carried out in the finishing stands, where the strip is located simultaneously in all 11 stands.
In the inter-stand spaces of the finishing group of stands there are also laminar-type inter-stand cooling units. The installation looks like a pipeline in which the nozzles are located. It is through them that the installation cools the strip at the desired temperature.
After the front end of the strip leaves the last finishing stand, the strip is directed at the filling speed along the discharge roller table to one of the coilers for coiling into a coil.
Three coilers are installed behind the finishing stands. In the fourth and fifth, thin strips with a thickness of 1.2 - 4 mm are wound into a roll, in the sixth - thicker strips from 2 to 16 mm. Before the strip enters the coiler, the pneumatic rulers are spread out and adjusted with a screw mechanism for setting to a solution that is 10-20 mm less than the sum of the nominal strip width and two strokes of the pneumatic ruler. After the strip is captured by the rollers, pneumatic cylinders bring the rulers together, which, with constant effort, center the strip throughout the entire winding process. After the end of winding, the rulers return to their original position.
Laminar-type strip cooling systems are located in front of each coiler, respectively, on the discharge roller table. The strip is cooled from above and below. After the strip is captured by the coiler, the winding of thin strips is usually carried out with tension without the participation of forming rollers, and thick strips are unwound with constant compression from the side of the forming rollers. After the strip has been coiled into a roll, the reel drum is stopped in a position that prevents the rear end of the strip from hanging down on the roll.
Further, after the release of the roll as a result of the compression of the reel drum, the rolls are transferred by a puller car to the contactor and the roll is stacked in a vertical position on the transfer car. The cart transports the roll to the conveyor.
Coil conveyors move the coil from the respective coiler groups to a turntable positioned some distance in front of the thick strip coilers. During transportation, the rolls are tied, weighed and marked. Then the rolls are transported by overhead cranes equipped with tongs to the finished product warehouse. They are then loaded onto wagons and sent to customers or cold rolling mills for further processing. Also on the territory of the workshop there are three cut-to-length units, which cut the finished product into measuring sheets.
The main technological equipment of the furnace department includes: methodical heating furnaces, a slab receiver, a device for stripping slabs, a loading roller table, a weighing roller table.
The methodical furnace is designed accordingly for heating the slab. The methodical furnace consists of a working space (hearth), where fuel is burned and the metal is heated, and a number of systems: heating, transportation of blanks, cooling of furnace elements, thermal management and others. The working space of the furnace is divided into zones: a methodical zone, a welding zone, a tormenting zone.
Figure 1. Plan of Rolling Shop - 4: Ґ ° - slab warehouse; Ґ ± - furnace department; VI - machine room; Ґі - finished goods warehouse; Ґµ - electric machine room; Ґ¶ - roll storage; Ґ · - rolling department. 1 - furnace roller table; 2 - slab pusher; 3 - receiving roller conveyor; 4-roughing group of stands; 5 - scale breaker; 6 - finishing group of stands; 7 - flying drum shears; 8 - winders; 9 - roll conveyor; 10 - heating furnaces.
All zones, except for the methodical one, are equipped with burners in which fuel (natural gas) is burned. The workpieces are heated gradually (methodically), moving, first through an unheated methodical zone (preheating zone), where the temperature is relatively low, then through welding (heating) zones with a high temperature, where the metal is rapidly heated, and the tormenting zone in which languor - equalization of temperatures along the section of the workpiece.
The slab receiver is designed for positioning the slab on the loading roller table and moving the slab from the loading roller table to the furnace; it is powered by an electric motor controlled by a frequency converter. The working stroke of the machine is calculated based on the slab width and the available space in the furnace. The slab receiver consists of a frame on which a trolley with rods is mounted for removing the slab from the furnace. The frame, in turn, is secured to a pivot bearing by means of a hinge. The trolley is mounted on a frame with the ability to move along the grooves made on the frame by means of rollers and is interconnected with a drive for its movement, made in the form of a hinged four-link, one link of which is a hydraulic cylinder. The frame is made in the form of a two-arm swinging arm, one end of which is connected to the slab lifting mechanism and is also a hinged four-link arm with a hydraulic cylinder.
The device for stripping slabs is designed to clean the upper surface of the slab from scale, dirt, debris and foreign objects with a roller brush before loading the slabs into the furnace. The device for stripping slabs consists of a working part with gas cutting heads, an idle roller table, a bed and a driving mechanism. Pneumatic cylinders mounted on calipers are used to expand the gas cutting heads in the vertical direction. In the horizontal direction, the gas cutting heads move together with the calipers.
The loading roller conveyor is designed for transportation of slabs coming from the existing slab warehouse. It consists of a frame, forged steel rollers, plates, an individual drive for each roller section, which consists of a geared motor.
The weighing roller conveyor weighs the slab on it using weight sensors installed under the frames of the weighing roller conveyor. It consists of a frame, rollers, plates, weighing system and slab position recognition. (2.s 115)
1.2 Design, operation and technical characteristics of the receiving roller table of heating furnaces
The receiving roller table of the heating furnaces is located in the furnace section of the hot rolling mill 2500 at the LPC - 4 OJSC MMK and is designed to receive heated slabs from the furnace and transport them to the working roller table in front of the roughing group of stands. The receiving roller conveyor at the furnaces consists of one two roller, fourteen three roller and three four roller sections. Each section consists of a frame and rollers. Frames are welded from sheet. The rollers are made of forging. The roller bearings are radial spherical double row roller bearings mounted in chocks. The cushions are installed in frames. The rollers are driven by a drive through a toothed clutch. The drive consists of a gear motor and a sub-engine plate. The engine plates are welded from sheet metal. The rollers are driven by a gear motor. The motor-reducer is made in a single housing due to which the motor shaft is the first shaft of the two-stage reducer.
Table 1 Technical characteristics of the receiving roller table near the furnace.
|
Characteristic |
The quantities |
||
|
Dimensions of transported metal |
|||
|
1000 ... 2350 mm |
|||
|
The largest mass of transported slab |
|||
|
The highest temperature of the transported slab |
|||
|
Roller barrel diameter |
|||
|
Roller barrel length |
|||
|
Step of rollers |
850,1050,1100,1300,1350,1500 mm |
||
|
Peripheral speed of rollers |
|||
|
Roller rotation frequency |
84.9 rpm |
||
|
Motor - reducer G82A ARC225M4 |
|||
|
Electric motor power |
|||
|
Reducer gear ratio |
Figure 2. Receiving roller conveyor at heating furnaces. 1 - geared motor, 2 - gear coupling, 3 - roller assembly, 4 - roller bearing, 5 - roller table section frame, 6 - sub-motor plate.
Figure 3. Kinematic diagram of the drive of the receiving roller table at the heating furnaces. 1 - motor - reducer, 2 - toothed coupling, 3 - roller, 4 - roller bearing.
1.3 Analysis of existing designs of roller tables for rolling mills
Roller tables are designed for transporting metal to a rolling mill, task of metal in rolls, receiving it from rolls and moving it to shears, saws, straightening and other machines. According to their purpose, roller tables are divided into workers and transport ones. Workers are roller tables located directly at the working stand of the mill and serving for the task of rolling metal into the rolls and receiving it from the rolls. Transport is the name for all other roller tables installed in front of the working stand and behind it and connecting the individual machines and devices of the mill.
Roller tables are distinguished with group and individual drive and idle rollers.
Figure 3. Roller conveyor with individual drive: a - from a flanged electric motor, b - from an electric motor through a gear coupling. 1 - roller, 2 - tapered roller bearings, 3 - cardan shaft, 4 - electric motor, 5 - plate of the electric motor.
With an individual drive, each roller of a given roller table section is driven by a separate electric motor. Such rollers are widely used in high-speed transport roller tables for moving rolls, the length of which after rolling is significant, as well as as the first rolls of working roll tables of crimping mills.
With a group drive, all rollers of one section of the roller table, consisting of 4 - 10 rollers or more, are driven by one electric motor through bevel gears and a transmission shaft. Roller tables with a group drive are used at a low speed of transportation over a relatively short distance. (3. P. 347)
Figure 4. Roller conveyor with group drive: 1 - roller frame, 2 - roller, 3 - bearing housing, 4 - bevel gears, 5 - transmission shaft, 6 - cylindrical gear, 7 - clutch, 8 - electric motor, 9 - rolling bearings, 10 - roller, 11 - roller bearings, 12 - cast covers, 13 - cast traverses.
The rollers of each section are driven by one electric motor through a clutch, two pairs of cylindrical gears, as well as bevel gears mounted on the transmission shaft and the ends of the roller journals. On the drive side, the rollers are mounted on tapered roller bearings enclosed in a housing. On the other hand, they, like the transmission shaft, are mounted on rolling bearings (2.с115)
1.4 Rules for the technical operation of roller tables
When accepting a shift, check the following:
Check if all the rollers are rotating; whether there is any runout in the rollers in the bearings; whether the inter-roller plates are not shifted and whether they come into contact with the rollers; serviceability of the fastening of the guide rulers; serviceability of roller cooling systems; the flow of grease to the friction units by the actuation of the feeders; oil level in gearboxes according to oil indicators; top up oil if necessary; the supply of thick and liquid grease to the bearings of the rollers, the transmission shaft, the shaft of the gearboxes. If necessary, adjust the amount of lubricant supplied to the friction units using the pistons of the feeders, as well as clean the oil channels and trays from contamination; through the inspection hatches in the gearbox covers, check the reliability of the gear wheels on the shafts, as well as the radial and axial clearances of the shafts in the bearings.
During the shift, the service personnel is obliged to monitor:
Operation of the equipment and remove pieces of metal (scrap), scale or other foreign objects from the roller tables; do not hold heated slabs or rolls on the rollers motionless. If the rolled metal for any reason is delayed on the roller table, then while waiting it should be moved along the roller table by "swaying" in order to avoid buckling of the rollers and unacceptable heating of the bearings; when placing slabs on a roller conveyor, avoid hitting the rollers; reversing the rollers smoothly; make sure that the rollers are cooled with water where it is provided; if necessary, the mill should stop the malfunctions; if there are any oil leaks from the gearboxes
Revisions and repairs of receiving and transport roller tables should be carried out once a month. Also check:
Condition and wear of roller barrels, bearing seats; replace rollers with wear on the barrel diameter of more than 20mm; Weakened bearing seats on the roller neck, transmission shafts, shafts of gearbox assemblies, gearbox housings and roller conveyor frames should be restored to drawing dimensions or parts should be restored; the level of the deck plates should be below the upper edge of the rollers by no more than 1/3 of the radius of the roller barrel from the side of the metal entrance; the gap between the rollers and the floor plates, the minimum allowable value of which is 10 mm; the condition of the frames of roller tables, gearbox housings and connecting traverses, if cracks and spalls are found on them that violate their strength and tightness, as well as when they are deformed, carry out the appropriate repair or replace; condition of gears, bearings, shafts, couplings, bolted and keyed connections. If necessary, carry out repairs or replace them. (5. From 24)
2. Special part
2.1 The choice of initial data and the power scheme for calculating the drive power of the receiving roller table at the furnaces of LPC - 4
Weight of one slab moving along the roller table Q = 18t = 180kN;
Roller weight G p = 3.97 t = 39.7 kN;
Roller barrel diameter d = 450mm = 0.45m;
Friction diameter in bearings d p = 190mm = 0.19m;
Slab speed along the roller table V = 2m / s;
The number of rollers in the roller table section driven by one el. dv. n = 1;
The condition of the metal transported on the roller table - hot slab;
The step between the rollers t = 1.1;
Figure 5. Power circuit for calculation
2.2 Calculation of the power of the electric motor of the drive of the roller table section of the heating furnaces LPC - 4
The moment from friction losses in bearings when moving metal along the roller table:
where: m p - coefficient of friction in the roller bearings m p = 0.005 - 0.008
Q m - slab weight per 4 rollers of one section;
Q ----------- 10m
Q m ---------- t
The moment from possible skidding of rollers on metal:
where: М beech - coefficient of roller friction during slipping, for hot metal М beech = 0.3
Static drive torque
M st = 0.025 + 0.731 = 0.756 kNm
Dynamic moment for metal transportation:
where: m p is the mass of the roller, (t)
m m - mass of metal, (t)
D ip - diameter of inertia of the rotating roller, (m)
Angular acceleration of the roller,
where: i is the acceleration of the metal moving along the rollers, for hot metal i = 3.0
Total torque of the roller table drive:
Roller table section drive power:
where: sh p ol - the angular speed of the rollers, (s -1)
Roller table drive efficiency.
since In the project, the electric motor is mounted in a single housing with a gearbox, then we choose a G82A ARC225 M4 gear motor with a power of N = 22 kW and a speed of n = 1450 rpm.
2.3 Kinematic calculation of the drive of the roller table section of heating furnaces LPC - 4
Let us determine the gear ratio of the roller table section drive for heating furnaces:
where: ww - the angular speed of the engine, s -1
We accept u p = 8.8 s -1 (see paragraph 2.2)
Determine the torque on the drive shaft of the roller table section of the heating furnaces:
Let us determine the torque on the output shaft of the roller table section drive of the heating furnaces:
2.4 Strength analysis of the main parts and assemblies of the roller table section
2.4.1 Checking calculation for the durability of the roller bearings of the roller table section
Let's define the distribution load acting on the roller:
Determine the reactions of the roller supports in the vertical plane:
Check:? F y = 0; Y a - G p + Y b - g m = 0
21532, 76 - 34640 + 21532, 76 -8425,53 = 0
Let's determine the reaction of the roller to bending, torsion:
We outline rolling bearings, double row with spherical rollers
No. 3538 d = 190, D = 340mm, C = 1,000,000 N, C o = 805000N
where: v - coefficient of rotation of the inner ring, v = 1.2
K t - at a temperature of 125 o C, K T = 1.45
Let's determine the estimated durability, mln. About:
Determine the estimated bearing life, hour:
where: n dv - engine speed, rpm.
Conclusion: the durability of the bearing of the drive of the receiving roller table is ensured.
2.4.2 Checking the strength of the rollers in the roller table section
Let's make a calculation for the dangerous section of the roller in the roller table section. A dangerous section of the roller is its center, it is there that the greatest loads and deformations in bending and torsion are observed. The torque in this section is 19483.85 Nm. Roller material 45 steel, heat treatment - improvement. With a roller diameter of 200 mm
Symmetrical bending cycle endurance limit:
Endurance limit at symmetric shear stress cycle:
Determine the safety factor:
with d = 200mm, b x h = 45 x 25 mm, t 1 = 15 mm.
Determine the moment of resistance to bending by the formula:
Determine the safety factor for normal stresses:
Let's determine the resulting safety factor of the roller:
Conclusion: S = 5.06> [S] = 2.5 The strength of the roller is ensured.
2.4.3 Calculation of the strength of the roller keyway
Prismatic keys with rounded ends. Dimensions of the length of keys and grooves in accordance with GOST 23360 - 78
Key material - steel 45 normalized.
Let us determine the shear stress and the strength condition of the keyed connection:
Permissible collapse stress with a steel hub [= 100 -120 MPa
d = 120mm, b x h = 28 x 16mm, t 1 = 10.0 mm
The strength of the keyed connection is ensured.
3. Organization of production
3.1 Organization of the repair service in the LPC - 4
The repair service of the workshop includes specialists responsible for the condition of all equipment in the workshop, including specialists from leading engineers to mechanics-repairmen. All personnel of the mechano-repair service in any workshop is divided into sections of the workshop. The functions of the personnel on duty include checking the health of pipelines and fittings, checking and tightening fasteners, checking the health of thick and liquid lubrication systems, checking oil leaks from crankcases or systems.
Figure 7. Scheme of the repair service of LLC "MSC" LPC-4.
The master is obliged:
Ensure that the site fulfills production targets in terms of the volume of production of products (works, services), quality, specified nomenclature (assortment), increasing labor productivity, reducing the labor intensity of products based on rational loading of equipment and the use of its technical capabilities, increasing the shift ratio of equipment, economical use of raw materials, materials, fuel, energy and cost reduction. Prepares production in a timely manner, ensures the placement of workers and teams, monitors the observance of technological processes, promptly identifies and eliminates the causes of their violation. Participates in the development of new and improvement of existing technological processes and production modes, as well as production schedules. Checks the quality of products or work performed, takes measures to prevent defects and improve the quality of products (works, services).
Takes part in the acceptance of completed works on the reconstruction of the site, repair of technological equipment, mechanization and automation of production processes and manual work. Organizes the introduction of advanced methods and techniques of labor, as well as forms of its organization, certification and rationalization of workplaces. Ensures that the workers fulfill the production standards, the correct use of production areas, equipment, office equipment (rigging and tools), uniform (rhythmic) work of the site. Carries out the formation of teams (their quantitative, professional and qualification composition), develops and implements measures for the rational maintenance of teams, coordinates their activities.
Establishes and timely brings production tasks to teams and individual workers (not part of the teams) in accordance with approved production plans and schedules, standard indicators for the use of equipment, raw materials, materials, tools, fuel, energy. Carries out production instructions for workers, takes measures to comply with the rules of labor protection, safety and industrial sanitation, technical operation of equipment and tools, as well as control over their observance.
Promotes the introduction of progressive forms of labor organization, makes proposals on revising production rates and prices, as well as on assigning worker categories to workers in accordance with the Unified Tariff and Qualification Reference Book of Work and Professions, takes part in the tariffication of work and the assignment of qualification categories to workers of the site. Analyzes the results of production activities, monitors the expenditure of the wage fund established by the site, ensures the correctness and timeliness of the preparation of primary documents for recording working hours, production, wages, downtime. Promotes the dissemination of best practices, the development of initiatives, the introduction of rationalization proposals and inventions. Provides timely revision of labor costs in the established manner, implementation of technically sound norms and standardized tasks, correct and effective application of salary and bonus systems.
Takes part in the implementation of work to identify production reserves in terms of quantity, quality and range of products, in the development of measures to create favorable working conditions, improve the organizational and technical culture of production, rational use of working time and production equipment. Monitors the observance by workers of labor protection and safety regulations, production and labor discipline, internal labor regulations, contributes to the creation of an atmosphere of mutual assistance and exactingness in the team, the development of a sense of responsibility and interest in the timely and high-quality execution of production tasks among workers. Prepares proposals on the encouragement of workers or the application of measures of material pressure, on the imposition of disciplinary sanctions on violators of production and labor discipline. Organizes work to improve the qualifications and professional skills of workers and foremen, train them in the second and related professions, conducts educational work in the team.
The foreman is obliged to: Organize work on the timely provision of workers with the necessary semi-finished products, materials. Places workers in their places. Monitors the quality of products, compliance with the technological process, the interconnection of operations, the correctness of accounting for the production of workers. Takes steps to eliminate equipment and worker downtime. If necessary, replaces workers. Eliminates the causes of product quality degradation. Ensures the fulfillment of the main planning tasks of the brigade, conveyor, flow (section). Monitors the timely and high-quality correction of product defects. Conducts instructions for workers on safety measures and the rules for the technical operation of equipment. Conducts an inventory of work in progress at the beginning and end of a shift. The foreman at the main production sites has the right to: Receive from the employees of the enterprise the information necessary to carry out his activities. Submit proposals on their activities for consideration by their immediate management.
Locksmith - repairman is obliged:
Disassembly, repair, assembly and testing of complex assemblies and mechanisms.
Repair, installation, dismantling, testing, regulation, adjustment of complex equipment, units and machines and delivery after repair.
Locksmith processing of parts and assemblies for 7-10 qualifications.
Manufacturing of complex fixtures for repair and installation.
Preparation of defective repair lists. Rigging with the use of lifting and transport mechanisms and special devices.
The locksmith-repairman has the right to give orders to his subordinate employees, assignments on a range of issues included in his functional duties. The locksmith-repairman has the right to control the execution of production tasks, the timely execution of individual orders by his subordinate employees. The locksmith-repairman has the right to request and receive the necessary materials and documents related to the issues of his activities and the activities of employees subordinate to him. The locksmith-repairman has the right to interact with other services of the enterprise on production and other issues that are part of his functional duties. The locksmith-repairman has the right to familiarize himself with the projects of decisions of the management of the enterprise concerning the activities of the unit. The locksmith-repairman has the right to propose for the manager's consideration proposals for improving the work related to the duties provided for in this Job Description.
The locksmith-repairman has the right to submit to the manager for consideration proposals on the encouragement of distinguished workers, the imposition of penalties on violators of production and labor discipline.
The locksmith-repairman has the right to report to the head about all violations and shortcomings in connection with the work performed.
The locksmith-repairman is responsible for violation of the rules and regulations governing the activities of the enterprise.
When transferring to another job or dismissing from office, the Repairman is responsible for the proper and timely delivery of cases to the person entering the current position, and in the absence of such, to the person replacing him or directly to his manager.
The locksmith-repairman is responsible for compliance with the current instructions, orders and orders for the preservation of commercial secrets and confidential information.
The locksmith-repairman is responsible for compliance with internal regulations, safety and fire safety rules.
3.2 Technology of carrying out repairs of metallurgical equipment. Repair documentation
All repairs of metallurgical equipment are divided into two types: current and overhaul.
Routine repair - repairs carried out to ensure or restore the performance of the product and the organization of repair facilities and equipment maintenance are based on the system of scheduled preventive maintenance (PPR).
Overhaul - complete disassembly of equipment and assemblies, detailed inspection, flushing, wiping, replacement and restoration of parts, check for technological accuracy of processing, restoration of power, performance according to standards and specifications.
Maintenance is a set of operations to maintain the operability of equipment when using it for its intended purpose, during storage and transportation. In the process of maintenance, periodically repeated operations - inspections, flushing, accuracy checks, etc. - are regulated and performed according to a pre-developed schedule.
Depending on the nature and scope of work performed during equipment stops for routine repairs, and on the duration of such stops, current repairs are divided into first (T 1), second (T 2), third (T 3) and fourth (T 4) current repairs. ... At the same time, for the same type of equipment, the scope of work of each previous (in order) type of repair is included in the scope of the subsequent one.
Overhaul is carried out to eliminate malfunctions and complete or close to full recovery of the equipment resource with replacement or restoration of any of its parts, including basic ones. The scope of work on overhaul also includes work on the modernization of equipment and the introduction of new technology, carried out according to previously developed and approved projects.
Overhaul is considered to be the repair of equipment with an established frequency of at least one year, in which they usually carry out a complete disassembly of the unit, replace or restore all worn out parts, assembly units and other structural elements, repair basic parts and foundations, assemble, verify, adjust and test the equipment without a load, and under load.
Normal operation of rolling equipment is governed by the technical operation rules developed and approved for all types of mechanical equipment of metallurgical plants.
To carry out equipment repairs at metallurgical plants, annual and monthly schedules of maintenance and repairs are drawn up. Annual schedules are drawn up by the department of management of the chief mechanic for all production shops on the basis of plans for the repair of the main technological equipment in the planned year.
For objects that are being prepared for overhaul, engineers and technicians of the mechanical services of rolling shops draw up a list of defects six to seven months before the start of the repair. The list of defects contains a list of units and main structural elements of the object with an indication of the repair work performed on them. It also indicates the machines, structural units and parts to be replaced, materials and spare parts required for repair.
To carry out current repairs, a repair sheet, an operational schedule, and a standard estimate are drawn up. Repair lists are compiled by the engineering and technical personnel of the shop's mechanical service. The repair list contains a list of mechanisms, repair work performed on them and replaced parts and assemblies, the number of assemblies and parts to be manufactured or restored, repaired, the amount of repair work and the required labor force are indicated.
The repair lists are handed over to the repair departments no later than 5 - 7 days before the start of the repair. Acceptance of equipment after repair is carried out by the personnel of the production department and is drawn up in an act drawn up after testing the equipment. (2.s 202)
3.3 Measures to improve the reliability and durability of parts and assemblies of metallurgical equipment
Reliability is the property of an object to perform specified functions under certain operating conditions. Distinguish between ideal, basic and operational reliability.
Durability is the property of an object to remain operational until the onset of a limiting state with an established system of maintenance and repairs. Durability is characterized by resource and service life.
An effective means of restoring worn out roller tables and increasing their wear resistance is automatic electric melting under a layer of flux. Cladding with conventional carbon wire allows reliable roll resizing. However, an incomparably more important task is to increase the durability of the rolls by surfacing a wear-resistant layer.
Electrofusion is a type of arc welding. Just as in welding, an electric arc burns between the product and the wire to which the current is supplied, melting the metal of the product and the wire.
With the help of automatic surfacing on the surface of products of different shapes, it is possible to apply a layer of metal of different thickness (1-40 mm), which is integral with the product. Due to the continuity of the process and the possibility of using high-strength welding current, automatic surfacing is 5-10 times more productive than manual surfacing.
To strengthen and increase the wear resistance of roller tables, a method of rolling a barrel with rollers is also used. The most perfect way to obtain high hardness of the working surface of cold rolling mills is quenching with high and industrial frequency currents.
With induction heating, roll warping is reduced and it is possible to obtain the required hardened layer thickness. After quenching, the rolls are subjected to grinding, during which they are calibrated. (10. P. 234)
3.4 Lubricating the roller table drive
The reliability of rolling equipment largely depends on the rational choice of lubricants, methods and modes of lubrication, quality control of lubricants during operation.
The main function of lubricants is to reduce frictional resistance and increase wear resistance and friction surfaces of parts. In addition, they remove heat from friction units and protect the lubricated surfaces from corrosion and rusting. The following types of lubricants are used to lubricate metallurgical equipment: liquid (mineral oils), plastic (greases), solid lubricants and lubricating coatings.
The friction units of the receiving roller table at the furnaces operate in difficult conditions caused by heavy loads, elevated temperatures, watering and contamination with abrasive particles from the environment.
Mineral oils are used in those friction units where liquid or semi-liquid friction can be provided, where forced heat removal or washing of rubbing surfaces is required.
Greases are used in open and unsealed friction units; in friction units where frequent lubrication changes are difficult or undesirable.
Lubrication methods are distinguished according to the principle of supplying lubricants to the contact surfaces in the deformation zone and the friction unit. When lubricating with liquid mineral oils, individual lubrication, oil immersion lubrication and pressure lubrication are used.
An individual lubrication method is used to lubricate individual parts and friction units when connection to centralized systems is difficult or specific requirements are imposed on them.
Dip lubrication is mainly used in gearboxes where the heat generated in the gearing is completely dissipated into the surrounding space through the crankcase wall or cover.
Pressure lubrication is the most efficient lubrication method. It is used in critical mechanisms and machines and is carried out using circulating lubrication systems.
When lubricating with lamellar materials, there are individual, embedded, centralized lubrication methods. In the individual method, lubrication is supplied periodically by means of hand-operated syringes through oilers installed in the lubrication holes. The mortgage method consists in filling the friction unit with grease during assembly or repair. The centralized method is used in the presence of a large number of friction units located far from the pumping station. (2. S227)
Table 2. Lubrication map of the receiving roller table for furnaces
Figure 6. Lubrication chart of the receiving roller table section: 1 - roller bearing, 2 - gear coupling
4. Labor protection
4.1 Measures for safety and fire protection in LPC - 4 of OJSC MMK
On the territory of sheet-rolling shop No. 4, safety measures are of particular importance. In the workshop, there are such harmful industrial hazards as: noise, dustiness, high temperatures, mobile vehicles, rotating mechanisms.
Dust in the air of the workshop is one of the factors of the working environment that determine the working conditions of workers. The causes of dust can be different: lack of sealing and aspiration of dust emission sources, the use of manual operations for transportation, loading and unloading of dry highly dispersed materials. The emission of dust into the air is also formed from cleaning equipment, air ducts, floors and gas lines by hand, brushes, brooms or blowing with compressed air.
Dust of larger fractions is formed between the rolls and the rolled metal, which is then carried away by the hot air and slowly settles on the equipment and structure of the shop. The size of dust 5 - 10 µm, which forms from the evaporation of the scale, is approximately 20%. This dust is carried throughout the entire workshop. Dust containing iron oxides affects the respiratory system. Penetrating deep into the respiratory tract, this dust can lead to the development of a specific disease - siderosis. Part of the dust, getting into the respiratory system, lingers on the nasal mucosa, and then gradually enters the oral cavity and digestive organs.
The main measures to combat dust are: the introduction of rational technological processes and equipment improvements, the use of effective sealing and aspiration of all dust-generating sources, dust moistening with water or steam; the device of special dust-collecting ventilation from places of dust formation with air purification before it is released into the atmosphere through a filter system, regular cleaning of workplace dust with special vacuum cleaners, the use of personal protective equipment (respirators, glasses, special clothes, etc.).
To suppress dust during rolling, the most effective method is hydro-dusting, in which it is possible to shrink up to 70 - 80% of the dust. Dust is deposited using nozzles.
Pneumatic dust extraction can significantly reduce or completely eliminate dust emission. At the same time, highly dispersed dust does not spread throughout the workshop, which is usually the case when sweeping or cleaning equipment with brushes. In addition, the use of pneumatic cleaning increases labor productivity by 25 - 30% and allows you to easily remove dust from walls, ceilings, metal structures, air ducts, equipment, hard-to-reach places that are rarely cleaned of dust with other methods and are sources of dust emissions.
An important factor in improving working conditions in the rolling industry is the reduction of industrial noise. The increase in the production intensity of the rolling speeds greatly increases the production noise in the rolling shops. Industrial noise of varying intensity and spectrum, long-term exposure to workers, leads to a decrease in hearing acuity, and sometimes to occupational deafness in workers.
To reduce noise in the source of its formation, it is necessary, if possible, to replace the shock interactions of parts with shockless ones, reciprocating movements with rotational ones, replacement of metal parts with parts made of plastics or other unsonic materials. Units that generate a lot of noise due to vortex formation or exhaust of air or gas, fans, pneumatic tools and machines must be equipped with special silencers.
Also, a huge danger for workers in the workshop is mobile transport. A huge number of carts move around the workshop territory, which transport finished products to warehouses, electric locomotives which every day bring and take away scrap metal or rolls from the workshop. In the aisles of the workshop, bridge cranes move, which have large load-gripping devices. Moving around the workshop, you need to take into account these dangerous factors. Failure to follow safety precautions can seriously injure workers. That is why there are special paths and bridges along which you need to move in order not to get hit by mobile vehicles. There are necessarily special helmets on the territory of the plant.
When working in places with elevated temperatures, people become dehydrated, sweat begins to flow profusely, and blood pressure rises.
That is why specials are provided on the territory of the plant. clothes, in the workshops there are coolers with salt water. (7. s58)
The furnace department of LPC - 4 belongs to the category of fire safety G. This category includes areas where non-combustible substances and materials are used in a hot, incandescent or molten state, the processing of which is accompanied by the release of radiant heat, sparks and flame, and (or) combustible gases, liquids and solids that are burned or disposed of as fuel. At the enterprises of ferrous metallurgy, the most effective, expedient fire extinguishing agents are used. The most widespread and cheapest means of extinguishing a fire is water, without which no metallurgical redistribution can work.
Water has a high heat capacity and therefore has a great cooling effect. The cooling effect of water is explained by the high heat of vaporization. In this case, a large amount of heat is taken away from the burning substance. Steam, in turn, reduces the oxygen content in the air, exhibiting insulating properties. It is known that some materials (cotton, textiles, soot and others, especially smoldering substances) are poorly wetted, therefore extinguishing them with water is ineffective. The fire extinguishing efficiency of water is increased by the introduction of surfactants and thickeners into it.
Water vapor is widely used in enterprises to extinguish fires in oil basements. To extinguish a fire with water vapor, where the fire has occurred, it is necessary to create a vapor concentration of 35%. For this, the oil basements are equipped with stationary dry pipes connected to the steam main. Dry pipes are laid in the lower part of the room, since the steam escaping from them will first of all begin to fill the upper volume of the oil basement.
Carbon dioxide is widely used to extinguish fires at an enterprise. It is a colorless and odorless gas. At a pressure of 6 MPa, it turns into a liquid state, in which it is stored in cylinders of carbon dioxide fire extinguishers. When leaving the fire extinguisher, turning into a gaseous state, carbon dioxide enormously increases its volume and cools down to -50 o С, cooling the burning substance and isolating it from air. Carbon dioxide is used in fire extinguishers and stationary installations to extinguish live electrical fires. Also, on the territories of ferrous metallurgy enterprises, there are fire shields on which there must be a fire bucket, a fire extinguisher, a box of sand. (11. from 297)
4.2 Environmental protection in the conditions of LPC - 4
To purify polluted air, devices of various designs are used, using various methods of cleaning from harmful substances.
The main parameters of gas cleaning devices and cleaning systems are efficiency and hydraulic resistance. Efficiency determines the concentration of harmful impurities at the outlet of the apparatus, and hydraulic resistance determines the energy consumption for passing the purified gases through the apparatus. The higher the efficiency and the lower the hydraulic resistance, the better.
Dust collectors, for cleaning exhaust gases from dust, there is a wide range of devices that can be divided into two large groups: dry and wet (scrubbers) - irrigated with water. Cyclones, the most widespread in the practice of bullet catching are cyclones of various types: single, battery.
Filters. In the technique of dust collection, filters are widely used, which provide a high efficiency of collecting small particles. The cleaning process consists in passing the cleaned air through a porous partition or a layer of porous material. According to the type of filter material, filters are divided into fibrous and granular fabrics.
In fabric filters, the filtering partition is a fabric (cotton, woolen, lavsan, nylon glass, metal) with a regular structure of weaving of threads (twill, linen, etc.). (8.c44)
Fiber filters are a layer of fine and ultra-fine fibers with an irregular, chaotic structure.
Sewage treatment
Industrial water is also used for cooling and cleaning equipment. In the 2500 mill, water is used to cool and wet the strip during the rolling process.
In the process of hot rolling, coolants are subject to contamination: by the smallest mechanical particles (impurities) released from the oxidized metal layer, by sludge after pickling and metal wear products; free (non-emulsified) oils released from the emulsion as a result of delamination; oils entering the mill emulsion system as a result of leaks from the mill mechanical and hydraulic equipment; oils washed off from hot-rolled strips pre-oiled before rolling.
Table 3. Analysis of waste coolant effluents of the 2500 mills.
The duration of the coolant (emulsion) cycle depends on the capacity of the emulsion system, the quality of cleaning.
Spent coolant (emulsion) is a special type of wastewater, very dangerous for water bodies, as it contains a large amount of stably emulsified oil products. The used cutting fluid contains 10 - 30 g / l of emulsified oils and a large amount of free oils. The total amount of ether-soluble substances in emulsion wastewater is 20-30 g / l.
Treatment of emulsion wastewater must necessarily include reagent treatment to destroy the emulsifier and emulsified oils. Sulfuric acid, hydrochloric acid, spent pickling solution are used as demulsifiers.
Treatment facilities are designed to remove free oils, mechanical impurities and oxidation products from the cooling circulating emulsion.
The structures of LPC - 4 of OJSC MMK provide for a 2-stage purification by settling and flotation, and include the following elements:
6 horizontal settling tanks equipped with scraper conveyors, 2 radial flotation machines, a pumping station with a pump for supplying flotation, pumps for supplying coolant to the 2500 mill, 2 receivers for settled and cleaned coolant, reagent facilities.
Figure 7. Wastewater treatment in the conditions of LPC-4: 1 - horizontal sump; 2 - receiving chamber of "dirty" emulsion; 3 - pressure tank; 4 - skimmer; 5 - receiving chamber of "pure" emulsion; 6 - pump 12D-9; 7 - pump 200D-60; 8 - pump 12NDS-60; 9 - automatic filter of the "SACK" system; 10 - tank of foam product from flotators; 11 - tank of foam product from sedimentation tanks; 12 - pump RZ-30; 13 - ejector
The spent coolant from the 2500 mill is fed through the distribution manifold to the receiving part of the horizontal sump designed to collect and remove the lightest fractions of oil and coarse mechanical particles (impurities). Then the coolant through the distribution baffle enters the settling chamber, where finer-grained mechanical impurities settle to the bottom. The settled coolant is collected in a chute and through a pipeline enters an intermediate receiver, then to a flotation unit for additional treatment. The settled coolant is pumped into the pressure tank, where the compressed air is dissolved in the emulsion. Then the mixture enters the water distribution mechanism and is evenly distributed over the entire cross section of the skimmer for the final purification of oil products. The cleaned coolant is discharged into a tray and enters the tank of the cleaned emulsion, and from there it is pumped out to the cold rolling shop for reuse. The oil products isolated in the settling tank and the flotator are discharged to the section for their regeneration. (8, p. 97)
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Technological process of LPC-3000. Technical characteristics of the equipment. Requirements for the original workpiece. Rolling technology on a two-stand mill. Cooling of rolls and shipment of products. Roller conveyor mechanism control. Furnace pusher automation.
practice report, added 06/18/2014
The problem of loading the furnaces of the sheet-rolling shop with hot slabs without waiting for them to cool down. The project of replacing the mechanical drive for lifting the table with a hydraulic one during the reconstruction. Energy-kinematic calculation and selection of the drive reducer.
thesis, added 11/09/2016
The main stages of the technological process of rolling production at a metallurgical plant, equipment of the technological line of the shop. Calculation of the number of main and auxiliary equipment in the shop, technical and economic selection of units and their capacity.
term paper, added 06/07/2010
Characteristics and purpose of the roller table - roller conveyor. The choice of the type of transporting machine, an increase in the mechanization coefficient in the production of boiled sausages, a decrease in the use of manual labor. Calculation of the conveyor, chain drive and bearings.
term paper, added 03/09/2010
Technological and technical characteristics of the main and auxiliary equipment of mill 350. Organization of work at the mill site. Metrological support for measuring the dimensions of rolled products. Drawing up a cost estimate for the rolling profile of a circle.
Introduction ................................................. ............................. 3
1 Brief overview of split mill rolls.
Mill 2500 characteristics. Mill assortment ............................ 4
1.1 Brief overview and analysis of the structure of the composite milling rolls. 4
1.2 Characteristics of hot rolling mill 2500 ....................................... 8
1.3 Mill assortment by steel grades and strip sizes ......................... 9
2 Research and development of the structure of a bandaged
back-up roll of hot rolling mill 2500 ........................................ 10
2.1 Choice of tightness, shape, band thickness and calculation
bearing capacity of the connection ............................................... .... ten
2.2 Calculation of stresses in a shrouded backup roll .................. 16
2.3 Calculation of the multiplicity of use of the axis of the split backup roll 30
2.4 Determination of cyclic endurance in section 1-1 .................. 33
2.5 Determination of cyclic endurance in section 2-2 .................. 36
2.6 Determination of the zone of slippage and deflection
integral and one-piece backup roll ............................................. 37
2.7 Determination of the deflection of a one-piece backup roll ............................... 37
2.8 Determination of deflection and slip zone for
split back-up roll ............................................... ............. 39
2.9 Developing measures to prevent fretting -
corrosion on upsetting surfaces and increased roll surface46
2.10 Investigation of the effect of coatings of mating coatings
on the bearing capacity of the connection axle - bandage.
Choice of material and coating technology ........................... 48
2.11 The choice of the material of the axle and the tire and the methods of their heat treatment. 52
4 Economic justification of the project .......................................... 57
4.1 Calculation of the production program ..................................... 57
4.2 Calculation of the capital cost estimate .......................................... 58
4.3 Organization of work and wages .............................. 59
4.4 Calculation of deductions for social needs .......................... 63
4.5 Calculation of the cost of production ...................................... 64
4.6 Calculation of the main technical and economic indicators ........... 65
Conclusion................................................. ........................ 68
List of sources used ....................................... 70
Introduction
The purpose of this thesis is to develop the design of composite back-up rolls, ensuring their reliability during operation, increasing their durability and reducing cost.
The rolls are the main element of the rolling stand, with the help of which the rolling strip is reduced. The requirements for rolling rolls are varied and relate not only to their operation, but also to the manufacturing process. The rolling roll works with the simultaneous action of rolling force, torque, temperature in the deformation zone, etc. on it. therefore, one of the main requirements is high wear resistance and thermal fatigue strength, which lead to low and uniform roll wear.
One of the ways to increase the durability of rolls and reduce their metal consumption is the use of composite rolls. The use of tires made of high-strength materials, the possibility of replacing worn-out tires with repeated use of the axle will give a great economic effect.
At present, in the 5.6 finishing stands of the 2500 mill of OJSC MMK, backup rolls 1600x2500 mm are used, which are made of forged steel 9HF. In this work, it is proposed to use composite rolls with a rim of cast steel 150KhNM or 35Kh5NMF. It is proposed to use used solid-forged rolls as axes. The experience of using rolls made of similar materials shows that their wear resistance is 2-2.5 times higher than that of forged rolls. The connection of the band with the axle is carried out according to the fit with a guaranteed interference fit. In order to increase the transmitted torque, it is proposed to apply a metal coating on the axle seating surface, which significantly increases the coefficient of friction, the area of actual contact between the axle and the tire and its thermal conductivity.
1 Brief overview of split mill rolls. Mill 2500 characteristics. Mill range.
1.1 Overview and Analysis of Composite Mill Roll Designs
The main advantages of composite rolls:
The ability to manufacture a tire and an axle from materials with different mechanical and thermophysical properties;
Possibility of replacing a worn-out band with repeated use of the roll axis;
Heat treatment of the axle band can be carried out separately, which makes it possible to increase the hardenability, to obtain the same hardness throughout the entire thickness of the band and to reduce the residual stress gradient, which is very high in a solid roll of large mass.
The production of bandaged backup rolls for sheet mills was mastered back in the 70s of the last century. The bandage and the axle are connected, as a rule, by a thermal method according to a fit with a guaranteed interference fit; Treads are made forged or cast, axles are forged; for their manufacture, discarded rolls are usually used. The hole in the band is most often cylindrical; the axle seat can be cylindrical, barrel-shaped, or close to it in shape to reduce the stress concentration at the ends of the band after assembly.
Composite rolls can be divided into the following groups according to the method of fastening the tires:
Using guaranteed interference fit;
Application of various mechanical methods of fastening the bandage;
The use of low-melting alloys and adhesive joints.
Many works of domestic and foreign scientists are devoted to the improvement of structures, methods of production and assembly, and the improvement of technological characteristics of composite rolls. Work to ensure a reliable connection between the tire and the axle takes an important place.
So, for example, in the work it is proposed to use a composite rolling roll containing a shroud with an interference fit, and superimposed on an axis with channels made in a spiral on the surface in contact with the shroud, and a shoulder. The paper proposes to use a roll with a composite shroud made of sintered tungsten carbide. In a number of works in recent years, it is more and more often proposed for use with weld-on tires made of high-alloyed alloys. In many cases, with the simplification of the roll manufacturing technology and the increase in the wear resistance of its surface, the cost increases significantly due to the use of a large number of alloying elements. Therefore, in order to increase the service life of the rolls, many authors devote their work to improving the design of composite mill rolls.
In the works, composite rolls are proposed, containing a bearing profiled axis and a band with a profiled inner surface, fitted with an interference fit with the possibility of free movement of its sections of a smaller diameter in a heated state along the bearing axis through sections with a large diameter along the length. Moreover, the generatrices of the surfaces of the axle barrel and the tire are profiled in the form of a smooth curve according to certain dependencies (Figure 1.2). The disadvantages of such rolls can be attributed to the complexity of their manufacture, the inability to control the required curvature of the profile of the landing surfaces, and in the case of the roll service life is also limited, caused by a small number of possible regrinds of the tire, due to the occurrence of tensile stresses in the middle part from heating and thermal expansion of the bearing axis in the process of rolling stand operation (Figure 2). But the main disadvantage can still be considered the complexity of the curves describing the profiles of the mating surfaces, which complicates the turning process, and the accuracy required for
their manufacture is practically impracticable with the technologies existing at machine-building plants.
Picture 1 - Composite milling roll
Picture 2 - Composite milling roll
In the work, in the conditions of the mill 2500 of OJSC MMK, it is proposed to use a composite backup roll, made in accordance with the diagram in Figure 3. The disadvantage of such a roll is the presence of a transition section of the axis from the shoulder to the tapered part, which is a stress increase concentrator, which can lead to breakage of the axis when increased loads and deflection, as well as limiting its service life. In addition, this design is not technologically advanced to manufacture.
Picture 3 - Composite milling roll
The task of the proposed manufacture of a composite back-up roll is the simplest technical solution that will increase the service life by ensuring a constant interference along the entire length of the mating surfaces.
It is proposed to make the seat of the tire and the axle cylindrical, from the point of view of simplicity and manufacturability. Make unloading chamfers - bevels on the axle edges to reduce stress concentration. To increase the bearing capacity of the joint and the roll performance, the main attention should be focused on the choice of the optimal interference value, the development of measures that significantly increase the coefficient of friction on the mating surfaces and the thermal conductivity of the axis - bandage contact.
When calculating strength, it is necessary to choose a technique that allows taking into account the effect of rolling forces on the stress-strain state of the tire.
1.2 Characteristics of hot rolling mill 2500
The 2500 hot strip mill consists of a charging section, a heating furnace section, a roughing and finishing group with an intermediate roller table between them and a coiling line.
The loading area consists of a slab storage and a loading roller table, 3 lifting tables with pushers.
The section of the heating furnaces consists of actually 6 heating methodical furnaces, a roller table in front of the furnaces with pushers and a sub-furnace roller table after the furnaces.
The roughing group consists of stands:
Reversible duo stand;
Expansion cage quarto;
Reversible universal quarto stand;
Universal quarto stand.
The finishing group includes flying shears, a finishing descaler (duo stand), 7 quarto stands. Devices for accelerated strip cooling (inter-stand cooling) are installed between the stands.
The intermediate roller conveyor ensures the discharge and cutting of defects (it is planned to equip the roller conveyor with thermal screens of the Encopanel type).
The coiling line includes a discharge roller conveyor with 30 sections for strip cooling (top and bottom spraying), four coilers, trolleys with lifting and rotating tables.
1.3 Mill assortment by steel grades and strip sizes
The 2500 wide strip mill is designed for hot rolling of strips of the following steels:
Carbon steel of ordinary quality in accordance with GOST 16523-89, 14637-89 steel grades in accordance with GOST 380-71 and current TU;
Steel welded for shipbuilding in accordance with GOST 5521-86;
High-quality structural carbon steel in accordance with GOST 1577-81, 4041-71, 16523-89, 9045-93 and current TU;
Alloy steel grade 65G in accordance with GOST 14959-70;
Low-alloy steel in accordance with GOST 19281-89;
Steel 7ХНМ according to TU 14-1-387-84;
Carbon steel and low-alloy steel of export performance according to TP, STP based on foreign standards.
Limit strip sizes:
Thickness 1.8 x 10 mm;
Width 1000 × 2350 mm;
Roll weight up to 25 tons.
2 Research and development of the design of a shrouded backup roll of a 2500 hot rolling mill
2.1 Choice of interference, shape, thickness of the band and calculation of the bearing capacity of the connection
The back-up roll of 5,6 stands of hot rolling mill 2500 of OJSC MMK, in accordance with Figure 4, has the following main dimensions:
Barrel length l = 2500 mm;
Maximum outer diameter of the barrel d = 1600 mm;
Minimum outer diameter d = 1480 mm;
The diameter of the necks at the junction with the barrel is 1100 mm;
The seat of the bandage is cylindrical. At a distance of 100 mm from each end of the axle, it is proposed to make 10 mm high relief chamfers to reduce the stress concentration of the tire after assembly. This is due to the fact that the band is connected to the axle by a thermal method, and when the joint is formed, the edges of the band cool faster than its middle part, which leads to the appearance of stress concentration and gives an additional opportunity for the development of fretting corrosion and fatigue cracks in the future.
Often, to prevent slipping of the band in the axial direction, a bead is made on the axis, and on the band there is a groove, or the seating surfaces are in the form of a cone. In this case, such devices are not used, since it is possible to assume that with a sufficiently large length of the mating surfaces, axial shear will not occur, and the strength of the joint will also be ensured by guaranteed interference and a possible increase in the coefficient of friction on the surfaces due to the application of a metal coating or abrasive powder to them. ...
Also, this design is much simpler and cheaper to manufacture.
Analysis of the factors influencing the choice of the landing diameter shows that the range of optimal values of the ratios of the landing and outer diameters fluctuates in the range d / d 2 = 0.5 ... 0.8.
If we talk about the choice of the joint tightness, then here you can run into disagreements. In practice, the optimal interference is usually taken equal to 0.8-1% of the landing diameter: D = (0.008? 0.01) d. Some authors advise increasing it to 1.3%, and some, on the contrary, lower it to 0.5%
For calculations, we will choose three different values of the tightness: D 1 = 0.8 mm; D 2 = 1.15 mm; D 3 = 1.3 mm.
Also, in order to compare and select the optimal connection criteria, we will perform calculations for different coefficients of friction and bandage thicknesses.
|
d landing1 = 1150 mm |
|
|
d landing2 = 1300 mm |
|
As mentioned above, the value of the coefficient of friction can be changed by applying any coating to the mating surfaces.
The greatest thickness of the shroud (d posad = 1150 mm) is caused by its passage through the necks of the rolling roll during assembly.
The d fit> 1300 mm is not taken into account, since upon reaching the minimum outer diameter (d 2 = 1480 mm) the band will become too thin.
Let's calculate some parameters of the bearing capacity of the connection under the given conditions.
- Highest axial force that a joint can withstand:
where K is the pressure on the landing surface, MPa;
F = pdl - seating surface area, mm 2; (d and l are the diameter and length of the seating surface, respectively, mm)
f is the coefficient of friction between the mating surfaces.
The pressure K on the seating surfaces depends on the tightness and wall thickness of the female and male parts.
According to the Lamé formula:
where D / d is the relative diametral interference;
q - coefficient.
where E 1 = E 2 = 2.1x10 5 N / mm 2 - moduli of elasticity of the axle and tire;
m 1 = m 2 = 0.3 - Poisson's ratios for steel axle and tire
С 1, С 2 - coefficients characterizing the thinness;
where d 1 and d 2 are the inner diameter of the axis and the outer diameter of the band, respectively.
For this case, there is no hole in the axis - d 1 = 0, and for the diameter d 2 we take the average roll diameter:
Then С 1 = 1 (d 1 = 0).
- Maximum torque transmitted by the connection:
- The compression stress in the axle is maximum on the inner surface:
On the inner surface of the bandage, the maximum tensile stresses are:
The calculation results are summarized in Table 1.
Conclusions: As you can see, the pressure K, and, consequently, the bearing capacity of the joint is proportional to the interference and inversely proportional to the coefficients C 1 and C 2, which characterize the thinness.
The difference in landing diameters is only 150 mm, but with the same interference fit, the difference in contact pressure is almost twice as large for a smaller diameter.
It should be noted that the compressive stress in the axle is also lower in the case for a thinner band, but the tensile stresses in the band remain practically unchanged with a change in its thickness.
Table 1 - Characteristics of the rolls of 5,6 stands of mill 2000 and their bearing capacity at various values of diameters, tightness, friction coefficients in the joint
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Metal pressure on rolls, t |
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Rolling moment, tm |
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Outer diameter of the band, mm |
d2 = 1600 (1480) dav = 1540 |
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Mating length, mm |
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Diameter of mating surfaces, mm |
d = 1150 (C2 = 3.52) |
d = 1300 (C2 = 5.96) |
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Landing surface area, mm |
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Tension, mm |
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Contact pressure, MPa |
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Roll axis stress, MPa |
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Bandage voltage, MPa |
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Friction coefficient f |
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The greatest axial force Ros, t |
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The greatest torque Mkr, tm |
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Picture 4 - Composite milling roll
With an increase in the friction coefficients, the bearing capacity of the joint also increases significantly, both in the case of d = 1150 mm and d = 1300 mm, but in the case of d = 1150 mm it is more maximal.
It is important that for all conditions, the connection ensures the transmission of torque with a good margin of safety.
M pr<М кр
Moreover, the safety margin increases with the growth of the contact pressure in the joint, caused by the interference.
In general, we can say that in both cases a good bearing capacity of the connection and rather low stresses in the roll parts are provided, but a shroud with an inner diameter of d = 1150 mm is more preferable, due to a significant increase in the same bearing capacity.
2.2 Calculation of stresses in a shrouded backup roll
The stresses in the composite back-up roll of the 2500 mill are determined for the same basic technical data specified in paragraph 2.1. It is required to determine the contact stresses on the seating surface of the tire and the axle.
The area of the band is denoted by S 2, and the area of the shaft by S. The radius of the mating surface after assembly is denoted by R, and the outer radius of the band is R 2.
On the outer contour of the band C 2, a force P is applied, equal in magnitude to the pressure of the metal on the rolls P 0. Taking P = P 0, we have a system of forces in equilibrium. The seating surface forms contour C.
The design scheme is shown in Figure 5.
Figure 5 - Design scheme for determining the contact stresses in the roll
When solving the problem, it is convenient to determine the stresses in polar coordinates. Our task is to determine:
s r - radial stresses
s q - tangential (circumferential) stresses
t r q - shear stresses.
Calculations of stress components are usually very cumbersome in general and in calculations. Using the N.I. Muskhelishvili in relation to the task and performing a solution similar to that given in the work, the stresses on the seating surface of the tire are determined in the form of formulas convenient for numerical implementation. The final expressions are:
where P = P 0 is the specific load per unit length of the band from the external force;
R is the radius of the contact surface;
h and g - series summed up in a closed form, reflecting the peculiarity of the solution in the zones of points of application of concentrated forces P and allowing to improve the convergence of the series;
q is the angular coordinate of the points of the contour C;
Constant Muskhelishvili;
m = 0.3 - Poisson's ratio;
a is the angle measured from the x-axis to the point of application of the force P;
n = R 2 / R - coefficient characterizing the thickness of the band.
The last terms in formulas (9) and (10) represent the stress components that depend on the tightness. Then the radial and tangential stresses in the composite roll are determined from two components, from the stresses caused by the interference and normal load:
sr =srp +srD (12)
sq =sqp +sqD (13)
Normal tension stresses are determined by the formula:
where K is the contact pressure from the interference (see Table 1), MPa;
n = R 2 / R is the relative thickness of the band.
Calculation of stresses s q D is carried out according to the following formula:
where d is half of the tightness;
E is the modulus of elasticity of the first kind.
As you know, there are no tangential stresses on surfaces from interference.
Then the stresses s rp, s q p and t r q can be represented as:
On a computer, the values of s rp, s q p and t r q were calculated for various values of n, some of which are given in Table 2.
The stress values are presented in the form of dimensionless coefficients C p, C q, C t, which should be multiplied by the value P / (R 2 x10 3), where P is the external load per unit length of the band, N / mm; R 2 - outer radius of the band.
To determine the stress components, it is only necessary to know n (the relative thickness of the band) and q (the polar angular coordinate of the point at which the stresses are determined).
In accordance with Figure 5, under the given conditions of equality to zero of the main vector and the main moment of force P, the stress diagrams at the contact are symmetric about the y-axis, that is, it is sufficient to determine the stresses in 2 out of 4 quarters, for example, in I and IV (from 3p / 2 to p / 2 rad).
The nature of stress distribution along the axis-band contact is shown in Figures 6, 7, 8.
Table 2 - Stress components and radial, tangential, tangential stresses on the seating surface of the tire from the action of the force P = 1200 kg / mm of stands 5,6, mill 2500
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N = 1.34 (d = 1150 mm) |
n = 1.19 (d = 1300 mm) |
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Figure 6
Figure 7
Figure 8
Analysis of the data obtained made it possible to reveal the following regularities: the smallest values of s rp are taken along the line of action of the concentrated force P together with its direct application q = 270 °. For some values of the angle q "295 ° for n = 1.34 and q" 188 ° for n = 1.19 the values of s rp change sign. Compressive stresses transform into tensile stresses that tend to break the solidity of the joint. Consequently, the diagrams s rp can have a certain physical interpretation: the contact points at which the stress signs change determine the areas of the joint opening zone in the absence of contact pressure from the interference due to the elastic deformation of the band.
The thinner the band, the more the maximal increase in srp at q = 270 ° and the greater the stress gradient in the region q = 260–280 °.
Tensile stresses, the greater, the thicker the band, but their gradient is insignificant, that is, the thinner the band, the greater the compression force on the axle.
On the diagrams of tangential stresses in the zone of action of the force P, it can be seen that s qр are tensile, and their maximum value practically does not depend on the thickness of the band. The stress gradient increases with decreasing thickness of the band, and the width of the zone decreases. On most of the contact surface of the axle and the shroud, the stresses are compressive with a smaller gradient for n = 1.34.
The plots of shear stresses t r q in Figure 9 change sign at points at q »215 ° and on most of the contact surfaces are tensile, but small for both cases, and, therefore, not too significant.
Table 3 shows the values of s r D and s q D for various values of D and n.
Table 3 - The magnitude of the contact pressure and tangential stress from the interference.
According to the data of Tables 2 and 3, we construct diagrams for s rp sr D and the resulting sr in accordance with Figure 9. Tangential stresses from the interference are different in sign for the contact stresses of the axle and the tire, therefore, consideration of the total diagrams on these surfaces must be performed separately (Figure 10, eleven).
The analysis of the stresses at the axle-tire contact of the composite roll shows that for any load scheme, the total contact pressure diagram differs significantly from the pressure diagram caused by the interference. Contact pressures are uniformly distributed around the circumference and have a high gradient in the zones of disturbance from the forces of metal pressure on the roll. In this case, the contact pressures from the interference make up only a part of the total contact pressure (in accordance with Figure 9) on a significant part of the contact. On a part of the contact surface, the total pressure is slightly less than the pressure from the interference.
Mpr? [Mkr] = P? f? R (19)
where Мпр - rolling moment;
Figure 9
Figure 10 - Diagrams s q p, s q D, s q on the contact surface of the axis of the backup roll of mill 2500 at P = 1200 kg / mm; n = 1.19; n = 1.34 and D = 0.8; 1.15; 1,3
Figure 11 - Diagrams s q p, s q D, s q on the contact surface of the backing roll shroud of mill 2500 at P = 1200 kg / mm; n = 1.19; n = 1.34 and D = 0.8; 1.15; 1,3
much of the contact. On a part of the contact surface, the total pressure is slightly less than the pressure from the interference.
The calculation of the roll for the possibility of turning the band on the axis from the action of the torque is made according to the formula:
Mpr? [Mkr] = P? f? R (19)
where Мпр - rolling moment;
[Mkr] - torque that can transmit the connection with an interference fit;
Р - contact pressure in the joint;
f is the coefficient of static friction on the seating surfaces of the joint;
R is the radius of the seating surface.
The allowable torque is directly proportional to the contact pressure, therefore, when calculating a composite roll for the ability to rotate the tire, it is necessary to take into account the distribution characteristics and the magnitude of the contact pressure in the rolls.
The total contact pressure in a composite roll is determined by the formula:
P =sr =srp +srD
By integrating s r in a circle, one can determine the limiting torque that a composite roll is capable of transmitting, taking into account the action of external forces P:
Calculations made according to this formula showed that the increase in the limiting torque that is capable of transmitting a composite roll without turning the band, taking into account the effect of external forces P, is approximately 20-25%.
The transmitted torque is proportional to the coefficient of friction f. The deformation of the roll under load also depends on the value of the coefficient of friction. Obviously, in order to prevent deformation and micro-displacements at the points of contact, it is possible to increase the coefficient of friction and create the required specific pressure at the contact. Changing the contact pressure can be achieved by changing the amount of interference and changing the thickness of the band. As can be seen from Figures 6, 7, 8, a decrease in the thickness of the band leads to an increase in stress gradients at the places of load application. And an increase in the tightness, in turn, leads to an increase in the stresses themselves, which, even at a value of D = 1.15 for d 2 = 1150 mm and D = 1.3 for d 2 = 1300 mm, exceed the allowable values for 150KhNM steel, equal to 200 MPa (Table 1), from which it is proposed to perform the bandage.
Therefore, it becomes obvious to increase the coefficient of friction on the seating surfaces. The optimal choice of the values of the interference value and the coefficient of friction will avoid surface wear, which will facilitate the reuse of the axle.
2.3 Calculation of the multiplicity of use of the axis of the composite backup roll
The axles of shrouded backup rolls are made from discarded, already used rolls. Therefore, the calculation for the frequency of use of the axis is based on the fatigue strength of its material - steel 9HF.
In the calculations,, the number of loading cycles, the fatigue characteristics of the axle material, as well as the values of 3 types of stresses were taken into account:
1 - compressive, caused by the fit of the tire on the axle with an interference fit;
2 - bending caused by metal pressure on the rolls;
3 - tangents caused by torsion.
The calculation was carried out for the most dangerous sections 1-1 and 2-2 (Figure 12) with different values of the interference fit.
Back-up roll 1600x2500 is transshipped in 5, 6 stands every 150 thousand tons of rolled stock. When regrinding, removal from the surface
Figure 12 - Schematic representation of sections for which the calculation of the roll axis for fatigue strength was made.
1-1 - cross-section of the middle of the roll barrel
2-2 - section, at the transition from the roll barrel to the neck.
barrels are produced at least 3 mm in diameter. The total removal is 120 mm (? Max = 1600 mm,? Min = 1080 mm), that is, the roll can be installed at least 40 times, for example, 20 in each stand
The main technological characteristics of 5, 6 finishing stands of the hot rolling mill 2500 of OJSC MMK are shown in Table 4.
Table 4 - Main characteristics of 5, 6 stands
In the calculations, we take the average rolling diameter of the backup roll d cf = 1540 mm.
The pressure of the metal on the rolls is constant, therefore, the maximum bending stresses s bend max are equal to s bend min, taken with the opposite sign. Compression stresses s compressed are also constant (Table 1), depending on the magnitude of the interference.
The calculations were made for three different values of the tightness D = 0.8; 1.15; 1.3.
Thus, the cyclic loading in all stands, which combines the action of constant and variable loads, is asymmetric.
The number of loading cycles in each stand is:
where V i - rolling speed in each stand, m / s;
d cf - the average rolling diameter of the back-up roll barrel, m;
t is the operating time of the roll in each stand for the installation, h;
K is the number of installations.
The calculation results are summarized in Table 5.
Table 5 - Number of operating hours and loading cycles in each stand
The total number of cycles of loading the backup roll with a single use of the axis is: N = SN i = 5.14x10 6.
2.4 Determination of cyclic endurance in section 1-1
Maximum bending stresses:
where P = 3000 tf is the metal pressure on the rolls;
a = 3.27 m - distance between the axes of the pressure screws;
W out = pd 2 axes / 32 - the moment of resistance of the section ost during bending;
L barrel = 2.5 m - length of the back-up roll barrel.
The maximum compressive stresses s compress are found by the formula (7). Therefore, we have:
Where j s - coefficient of metal sensitivity to cycle asymmetry;
s 0 = (1.4 ... 1.6) s -1 - fatigue limit for a pulsating cycle.
The maximum stress caused by torsion t maxi in each stand depends on the maximum torque M cr i = 217 tm:
Equivalent stress, taking into account all types of stresses acting on a composite roll:
The calculation results are summarized in Table 6.
Table 6 - Values of stresses in the roll for various values of the landing diameters and interference
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Landing diameter, m |
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s out, MPa |
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Tension, mm |
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s eq, MPa |
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The corresponding number of cycles that the sample can withstand before failure is:
Axle material - steel 9HF, with the following fatigue characteristics:
s -1 = 317 MPa - endurance limit;
N 0 = 10 6 - the basic number of cycles;
R = tga = (0.276s -1 -0.8) = 7.95 kg / mm 2 - the tangent of the slope of the fatigue curve
To assess the margin of durability and the service life of a part when calculating for a limited durability, the criterion n extra long is applied. - permissible margin of durability:
where n add = 1.5 is the permissible margin of safety.
The multiplicity of using the axis with full use of the strength properties of the material:
The calculation results are summarized in Table 7.
Table 7 - Influence of the bore diameter and axle tightness on its multiplicity
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Landing diameter, m |
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Tension, mm |
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T-axis multiplicity |
||||||
Based on the calculations performed, the following conclusions can be drawn: with an increase in the interference, the multiplicity of using the axis of the composite backup roll decreases due to an increase in constant compressive stresses caused by shrinking the tire on the axle with an interference fit. In the case of a thinner tire (d = 1.13 m), an increase in the axle utilization rate is observed by more than 3 times at the same preload values, since d = 1.13 m is characterized by lower axle compression stresses. If we turn to the diagrams of stress distribution for different thicknesses of the band (Figures 6, 7, 8, 9, 10, 11), we should note a less favorable picture for a thinner band. It should also be taken into account that the calculations took into account not only the maximum allowable roll loads, but their peak values. Considering that for steel 150KhNM, from which it is proposed to make a bandage, the tensile stresses in the bandage exceed the allowable ones in cases d = 1.15 m at D = 1.15 mm and d = 1.3 m at D = 1.3 mm (Table .1), then the optimal variant can be considered with d = 1.15 m, D = 0.8. The multiplicity of the axis in this case is 2.45 times. But, taking into account that the real loads are somewhat less than the calculated ones, and also that it is proposed to apply a metal coating on the mating surfaces, which increases the bearing capacity of the joint without significantly changing its stress state, the frequency of using the axis will naturally increase.
2.5 Determination of cyclic endurance in section 2-2
The axis of the supporting composite roll in section 2-2 experiences bending and tangential stresses. With this loading, the stresses change in a symmetric cycle:
There is no danger of axle fatigue failure in this section.
2.6 Determination of the slip and deflection zone of a composite and one-piece backup roll
It is known that in the course of work, as a result of the applied loads, both the work rolls and the backup rolls begin to bend. The deflection phenomenon can cause a deterioration in the quality of the rolled strip, roll runout, which, in turn, can lead to a quick failure of bearing assemblies and the appearance of fretting corrosion.
The temperature difference between the band and the axle during rolling, in the case of a composite roll, can lead to rotation of the band relative to the axis, that is, the appearance of a slip zone.
Below are calculations of the possible size of the slip zone, taking into account the existing loads and determining the deflection of a composite and one-piece backup roll in order to compare their values.
2.7 Determination of Deflection of One-Piece Back-up Roll
The pressure of the metal on the rolls during rolling is transferred through the work rolls to the support rolls. The nature of the pressure distribution along the barrel of the backup rolls depends on the width of the roll, the rigidity and length of the barrel of the work and backup rolls, as well as on their profile.
If we assume that the pressure of the metal on the rolls is transferred by the work roll to the support roll evenly, then the deflection of the support rolls can be calculated as the bending of a beam freely lying on two supports, taking into account the action of transverse forces.
Total boom of backup roll deflection:
f o.v. =f o.n. =f 1 +f 2 (32)
where f 1 - boom deflection from the action of bending moments;
f 2 - boom deflection from the action of transverse forces.
In turn
where P is the pressure of the metal on the roll;
E is the modulus of elasticity of the roll metal;
G is the shear modulus of the roll metal;
D 0 - the diameter of the backup roll;
d 0 - diameter of the neck of the backup roll;
L is the length of the back-up roll barrel;
a 1 is the distance between the axes of the bearings of the backup rolls;
c is the distance from the edge of the barrel to the bearing axis of the back-up roll.
Table 8 - Data for calculating the deflection of a solid backup roll
|
Name |
Designation |
Meaning |
|
Metal pressure on the roll, N |
||
|
Modulus of elasticity of the roll metal, N / mm 2 |
||
|
Roll metal shear modulus, N / m 2 |
||
|
Back-up roll diameter, mm |
||
|
Back-up roll neck diameter, mm |
||
|
Back-up roll neck length, mm |
||
|
Continuation of table 8 |
||
|
Distance between bearing axes, mm |
||
|
Distance from the edge of the barrel to the bearings, mm |
||
|
Deflection due to bending moments, mm |
||
|
Deflection due to shear forces, mm |
||
Then the total boom of the back-up roll deflection is:
f = 0.30622 + 0.16769 = 0.47391 mm
2.8 Determination of Deflection and Creep Zone for a Split Back-up Roll
The main data for the calculation are shown in Table 9.
Table 9 - data for calculating the stiffness of the composite back-up roll
|
Index |
Designation |
Meaning |
|
Bandage radius, m |
||
|
Axis radius, m |
||
|
Modulus of elasticity of the first kind, N / m 2 |
||
|
Modulus of elasticity of the second kind, N / m 2 |
||
|
Coefficient taking into account the uneven distribution of shear stresses |
||
|
Coefficient taking into account the design of the band edges |
||
|
Coefficient depending on the cross-section of the axis |
||
|
Coefficient depending on the cross-section of the band |
||
|
Continuation of table 9 |
||
|
Poisson's ratio |
||
|
Tension between the bandage and the roll axis, m |
||
|
The coefficient of influence of the axle parts protruding along the edges of the bandage |
||
|
Friction coefficient |
||
|
Torque, Nm |
||
|
Back-up roll barrel length, m |
||
|
Effort of impact on the roll, N |
||
|
Roll neck radius, m |
||
|
Roll neck length, m |
||
|
Neck factor |
||
Cross-sectional area of the band and axis:
Moments of inertia of the tire and axle:
Constant coefficient:
Contact pressure P H = 32.32x10 6 N / m 2 (see Table 1).
Bending moment per unit length due to frictional forces:
m = 4mP HR 2 = 12822960 Nm (39)
Calculation of the length of the slip section of the tire relative to the axis during bending:
Determine the deflection of the composite back-up roll, using the technique given in the work,. The design scheme is shown in Figure 13.
Figure 13 - Scheme of the acting forces in the axial section of the shrouded roll
Bending moment acting on the roll in section:
Shearing force acting on the roll in section:
Q 0 =q 0 (l 0 -l) = 10.23x10 6 N (45)
Determination of the deflection at [x = 0]:
Rotation angle at [x = 0]:
The intensity of the force of interaction between the axle and the tire:
Determination of deflections for the tire and the axle in the slip area:
Tread and axis rotation angles:
Bending moment on the band and axle:
Shearing force acting on the tire and axle:
Shroud displacement relative to the axis at the edge of the roll barrel:
Roll neck deflection:
Full deflection of the shrouded roll:
y =y x +y w = 0.000622 m = 0.622 mm(65)
As can be seen from the calculation results, the deflections of the composite and solid rolls under load are practically the same. The deflection of a composite roll is slightly more than that of a solid roll (y solid = 0.474 mm, y st = 0.622 mm). This suggests that the stiffness of the composite roll is lower, as a result of which the band can slide about the axis. Calculations, in turn, showed that the slip zone is small and is only 0.045 m. The size of the slip zone and the roll stiffness as a whole are influenced by the circumferential tensile stresses in the sleeve s t (in accordance with Figure 13).
Experiments carried out to study the stiffness of composite rolling rolls made it possible to see that the greatest tensile stresses s t are located on the inner contour of the tire in the area of its contact with the shaft; this indicates an increase in contact pressures from seating when the roll is bent. It was found that a decrease in the relative tightness reduces the stress s t. Consequently, reducing the tightness of the press connection can eliminate the destruction of the tire, however, this leads to a loss of stiffness of the shaft, weakens the press connection, expands the slipping area of the tire and promotes fretting corrosion of the seating surface. Since the minimum preload value (D = 0.8 mm) was chosen for the calculations, in order to improve the adhesion of the shaft to the shroud, it is necessary to increase the coefficient of friction on the seating surface, for example, by applying a metal coating.
2.9 Development of measures to prevent fretting - corrosion on sedimentary surfaces and increase the roll surface
Fretting - corrosion - damage to a metal surface as a result of contact friction, in which separated particles and surface layers interact with environmental components (most often with oxygen).
It is known that with the smallest loads on the contacting surfaces, noticeable damage to the surface layers from fretting can occur. This fully applies to composite rolling rolls assembled by interference fit, in which contact pressures reach significant values and there are slip zones adjacent to the ends of the band. At the mating points with alternating displacements of the axle and tire seating surfaces, scuffs are formed, the number of which increases almost in proportion to the interference tension. Subsequently, they pass into stress concentrators, which causes accelerated fatigue failure of the axis located at a certain distance from the end of the tire along the seating surface. Typically, in roll designs that exhibit fretting corrosion, failure occurs here and not along the neck. In order to reduce the influence of this process at the ends of the axle, destructive chamfers are performed in order to increase the reliability of the axle by removing stress concentrators, which at the edge of the interface become equal to zero (Figure 14).
Figure 14 - Bevels at the edge of the axis of the shrouded roll
However, without special types of processing of the seating surfaces, it is impossible to avoid axle breakages for this reason. The most effective in this case are soft galvanic coatings. Their use significantly increases the area of the actual mating contact. In this case, strong bonds appear in the contact of the mating parts (seizure of metals), due to which the metal surfaces of the mating parts are protected from scoring and mechanical damage. At the same time, the likelihood of residual deflection is sharply reduced, and the prerequisites for repeated use of the axle with replaceable tires increase.
2.10 Investigation of the effect of coatings of mating coatings on the bearing capacity of the axis-band connection. Choice of material and coating technology.
The bearing capacity of an interference joint is directly proportional to the coefficient of friction on the seating surface, which is included in the basic design formulas for determining the highest torques and axial forces. The coefficient of friction depends on many factors: the pressure on the contact surfaces, the size and profile of microroughnesses, the material and condition of the mating surfaces, and the assembly method. It should be noted that for large diameters (d = 500 - 1000 mm) of the seating surfaces and, accordingly, the interference fit (up to 0.001 d), which are typical for the design of composite rolls, there are no experimental data on the magnitude of the friction coefficients. Usually, when calculating composite rolls, the assembly of which is carried out by heating the tire to 300-400 ° C, the friction coefficient is taken equal to f = 0.14. Such caution and the choice of a very low value of the coefficient of friction are quite justified. The fact is that at large values of the interference (up to 1 - 1.3 mm), the effect of the initial roughness of the surface and the oxide films formed on it when the band is heated, increasing the friction coefficient, can turn out to be very insignificant.
A number of works indicate that the bearing capacity of interference joints can be significantly increased by applying galvanic coatings to one of the seating surfaces. The thickness of the coatings is usually 0.01 - 0.02 mm. On average, the use of coatings increases the friction coefficients by one and a half to four times for all assembly methods.
The increase in the strength of joints with galvanic coatings is explained by the occurrence of metallic bonds in the contact zone and an increase in the actual contact area. It was revealed that soft galvanic coatings, even at low pressures, undergo plastic deformations and fill the depressions of the micro-profile of the covered part without causing its plastic deformation. An increase in the strength of the joints is caused by the fact that at the initial moment of displacement of the parts, there is a simultaneous shearing of a large number of microvolumes of the coating by the irregularities of the covered part. Soft (anodic) coatings (zinc, cadmium, etc.) have the most favorable effect on the bearing capacity of cylindrical joints with interference. They contribute not only to the strength of the joints, but also to the resistance to fatigue of the shafts. Zinc plating increases the circumferential endurance of the shafts by 20%.
When coating is applied, the interference in the joint increases. Usually, the preload increment is taken to be equal to the doubled thickness of the coating, regardless of its type. It should be noted that at high interference and large diameters of the joint, the effect of the coating thickness is not so significant.
An analysis of the results of works in which the effect of coatings on the bearing capacity of joints with an interference fit is considered suggests that a coating of sufficiently ductile metals is most suitable for composite rolls. The application of such coatings to the axle seating surface makes it possible to increase the friction coefficient by at least 2 times. When choosing a coating method and technologies, we will be guided by the following considerations.
There are a variety of metal coating methods to prevent corrosion, heat, reduce wear, etc. Almost all coating methods (hot, electrolytic, spraying, chemical deposition, etc.) require surface preparation, usually including degreasing, etching , chemical and electrochemical polishing. These operations are harmful to the operating personnel and, despite the thorough cleaning of the effluent, they pollute the environment.
The use of these methods for coating the axle of a composite mill roll with a length of about 5 meters presents significant technical difficulties. It should be noted that in works that provide data on the effect of coatings on the coefficient of friction, coatings were applied electrolytically or hot to small samples or models of rolling rolls. The use of such methods for large-sized rolls will require the creation of special departments or workshops. It seems expedient to use frictional coating methods. One of the simplest and most effective is the method of coating with a rotating metal brush (VMSh, friction cladding). In this case, surface plastic deformation (SPD) occurs simultaneously with the deposition of the coating, which will increase the fatigue strength of the roll axis.
A schematic diagram of one of the options for applying a coating with a rotating metal brush is shown in Figure 14.
The coating material (MP) is pressed against the VMSch pile and heats up in the contact zone with it to a high temperature with it. Particles of the coating metal are seized with the ends of the villi and transferred to the surface to be treated. The surface of the workpiece is hardened due to intense plastic deformation by flexible elastic elements. At the same time, plastic deformation of the coating metal particles located at the ends of the villi occurs and their seizure with the surface of the product occurs. Removal of oxide films, exposure of clean surfaces during joint plastic deformation of the surface layers and particles of the coating material ensures their strong adhesion to the base.
Figure 14 - Scheme of coating by friction cladding (FP)
1- blank from coating material (MP)
2- tool with flexible elastic elements (VMSh)
3- work piece (axis of the compound roll)
The coating that is applied to the mounting surface of the roll axis must have the following properties: significantly increase the coefficient of friction, be sufficiently plastic and fill the depressions of the micro-profile, and have good thermal conductivity. Aluminum can meet these requirements. It is well applied to the steel surface using VMSH and forms a coating of sufficient thickness. However, the answer to the main question - about the value of the coefficient of friction in a joint with an interference fit, one of the mating surfaces of which is coated with aluminum, is absent in the technical literature. Cylindrical joints made of steel - aluminum materials, assembled with an interference fit, are also not known, since pure aluminum, due to its low strength characteristics, is not used as a structural material. However, there is data on the coefficients of friction during plastic deformation of metals (table 10).
Table 10 - Coefficients of dry friction of various metals on steel grade EKh-12 with hardness HB-650
|
Brass L-59 |
Aluminum |
|||||||
|
Average value of the coefficient of friction |
As follows from table 10, aluminum under plastic deformation has a maximum coefficient of friction in contact with the rest of the surface. In addition, aluminum has a very high thermal conductivity. These factors were the reason for choosing aluminum as a coating material for the male surface of the roll axis.
2.11 Selection of axle and tire material and methods of their heat treatment
When choosing a material for composite rolls, the thermomechanical conditions of their service should be taken into account. The rolls are subjected to significant static and shock loads, as well as thermal effects. Under such harsh operating conditions, it is very difficult to choose a material that provides both high strength and wear resistance.
Different requirements are imposed on the roll barrel and roll core. The core must have sufficient toughness and strength, well resist bending, torque and shock loads. The surface of the barrel must have sufficient hardness, wear resistance, and heat resistance.
The roll axis is made of 9KhF steel, the roll band is 150KhNM, based on the experience of using this steel in the manufacture of composite rolls at OJSC MMK. It is proposed to use a more alloyed steel - 35Х5НМФ as the material of the bandage, which has a higher wear resistance in comparison with 150ХНМ. The data on the wear resistance of roll materials under hot rolling conditions are presented in table 11.
Table 11 - Mechanical properties and wear resistance of roll materials.
|
steel grade |
Approximate chemical composition |
Mechanical properties |
Relative wear resistance |
||
|
Hardness |
s B, kg / cm 2 |
s t, kg / cm 2 |
|||
|
0.08-0.9% C, 0.15-0.3% V, 0.15-0.35% Si, 0.3-0.6Mn, 0.4-0.6% Cr, S, P? 0.03% |
|||||
|
0.5-0.6% C, Ni? 1.5%, S, P? 0.03% |
|||||
|
1.4-1.6% C, 0.8-1.2% Ni, 0.5-0.8% Mn, 0.25-0.5% Si, 0.9-1.25% Cr, S, P? 0.04% |
|||||
|
0.3-0.4% C, 5% Cr, Ni? 1.5%, Mn? 1.5%, Y? 1.5%, S, P? 0.04 |
|||||
It follows from the table that steels 60ХН 9ХН, which are used mainly for vertical and horizontal rolls of the roughing group, have the lowest relative wear resistance, which is confirmed by the experience of their operation. But these steels by their characteristics are quite suitable for the manufacture of axles of composite rolls. For the manufacture of cast bandages, it seems appropriate to use steel 150KhNM 35Kh5NMF.
35Kh5NMF has a higher cost compared to 150KhNM, but, having significant strength and wear resistance, it pays for itself during operation, since, providing increased resistance to wear and spalling, it retains a good structure of the roll barrel surface for a longer time.
To give the tires and axles the required operational properties, they are first separately heat-treated. Then the band, heated to a certain temperature, which provides a sufficiently free fit on the profiled axle, is formed by a press fit (during cooling, the axle is wrapped).
These technological operations lead to the formation of significant residual stresses in the band from heat treatment. Cases are known when, due to the high level of the indicated stresses, the tires were destroyed even before the start of operation: during storage or transportation.
According to the operating conditions, the axles are not subject to high requirements for hardness (230? 280HB), while the requirements for tires are more stringent (55? 88HSD). In this regard, for the axles, a softer heat treatment is applied in comparison with the tires, which does not lead to the occurrence of significant residual stresses. In addition, tensile stresses from landing, which are dangerous from the point of view of brittle strength, arise only in the tire, as a result of which a fracture can occur along the roll barrel.
As the experience of heat treatment of these steels in the manufacture of tires shows, the most effective treatment is triple normalization at temperatures of 1050 ° C, 850 ° C and 900 ° C, followed by tempering, which provides the most favorable combination of plastic and strength characteristics.
Triple normalization maintains the inherited cast structure and promotes the distribution of properties that provide increased resistance to wear and chipping.
The roll axis is made from a used roll. After regrinding to the required size, an aluminum coating with a thickness of about 20-25 microns is applied to the axle seating surface by a friction method. Finish the seating surface before coating - clean sanding.
Thermal assembly significantly (1.2-1.5 times on average) increases the load-carrying capacity of joints with interference. This is due to the fact that when assembling under a press, microroughnesses are crumpled, while during thermal assembly, they, closing, go into each other, which increases the coefficient of friction and adhesion strength. In this case, the particles of the coating penetrate both the surface of the axle and the band, mutual diffusion of the atoms of the coating and the base metal occurs, which makes the connection practically monolithic.
Therefore, in the connection, it is possible to reduce the preload required to transmit a given torque, with a corresponding decrease in stresses in the axle and tire.
With a sufficiently high heating of the band, it is possible to obtain zero interference or to provide a gap when assembling the joint. The recommended heating temperature of the shroud before assembling the roll is 380 ° C-400 ° C.
The following methods of replacing worn-out bandages are possible:
- Mechanical - along the generatrix of the band for its entire thickness, two slots are made on a planer or milling machine, as a result of which the band is divided into two halves that can be easily dismantled. The slots are located diametrically opposite to one another.
- Heating of the band in the inductor to industrial frequency currents (TFC) - the band is heated up to 400 ° С-450 ° С. this temperature is reached in three to four transitions of the inductor within 15-20 minutes. When the band is heated along the section to the specified temperature, it falls off the seating surface.
- Dismantling the bandage using an explosion - this technology was used at MMK back in the 50s of the last century. In 1953, the 1450 hot rolling mill was completely transferred to composite backup rolls. The worn out bandages are removed from the axle by the explosion of small charges placed in the drilled holes. This technology is possible in the conditions of the city of Magnitogorsk.
4 Business case for the project
OJSC MMK is the largest metallurgical plant in our country. Its main task is to fully meet the market needs for high quality products. Shop LPC-4 is part of MMK, which is a joint stock company. The development of the plant does not stand still: the methods of metal processing are being improved, new ideas are being introduced, and modern equipment is being purchased.
The modernization of mill 2500 at LPC-4 of OJSC MMK is carried out by replacing solid rolls with shrouded rolls. The cost of one shrouded roll is 1.8 million rubles, while the annual consumption of rolls is 10 pcs. The cost of shrouded rolls is 60% of the cost of solid ones, while due to the use of a more wear-resistant material for the shroud, the annual consumption of rolls will decrease by 1.6 times and will be 6 pcs. in year.
4.1 Calculation of the production program
Drawing up a production program begins with calculating the balance of the operating time of the equipment in the planned period.
The actual operating time of the equipment is calculated by the formula:
T f = T nom * C * T c * (1-T tp / 100%)(66)
where C = 2 is the number of shifts of equipment operation,
T c = 12 - the duration of one shift,
T tp - the percentage of current downtime in relation to the nominal time (8.10%),
T nom - the nominal operating time of the equipment, calculated by the formula:
T nom = T cal -T rp -T p.pr -T in (67)
where T cal = 365 days. - calendar fund of equipment operation time,
T rp = 18.8 days. - operational downtime;
T p.pr = 12 - the number of days the equipment is on scheduled preventive maintenance,
T in - the total number of holidays and days off in a year.
T in = 0, since the work schedule is continuous.
Annual production is calculated as:
Qyear= P cf * T f (68)
Where P cf = 136.06 t / h - average hourly productivity.
The actual operating time of the equipment and the annual production:
T nom = 365-18.8-12-0 = 334.2 (days)
T tp = 0.081 * 334.2 = 27.7 (days) or 650 (h)
T f = 334.2 * 2 * 12 * (1-8.1 / 100) = 7371 (h)
Q year = 136.06 * 5033 = 1002870 t
The calculated data are shown in table 12.
Table 12 - Balance of equipment operation time
4.2 Calculation of the capital cost estimate
The cost of modernizing mill 2500 is calculated using the formula:
K z = C about + M + D ± O-L(69)
where M is the cost of equipment installation,
D - the cost of dismantling the equipment,
О - residual value of dismantled equipment
L - liquidation value (at the price of scrap metal), calculated as:
L =m* C l(70)
where m is the mass of the dismantled equipment,
C l - the price of 1 ton of scrap metal,
From about - the cost of the purchased equipment.
Then the costs for the purchase of rolls will be:
With about = 6 * (1,800,000 * 0.6) = 6,480,000 rubles.
The costs of dismantling old and installing new rolls are zero, since the change of rolls is an ongoing job in the shop: M = D = 0 rubles.
There is a replacement of solid rolls, already worn out, respectively, their residual value O = 0 rubles.
The worn out solid rolls are recycled, therefore they do not have any salvage value (L = 0).
Thus, the capital costs for the implementation of the modernization:
K z = 6480000 + 0 + 0 + 0-0 = 6480000 rubles.
4.3 Organization of work and wages
The calculation of the wage fund is shown in Table 13.
Table 13 - Calculation of the wage fund
|
Indicator name |
Worker name |
|||||||||
|
Master (senior) |
Foreman |
Crane operator |
Roller |
Post operator |
||||||
|
Attitude towards production |
||||||||||
|
Rank of work or salary |
||||||||||
|
Tariff grid |
||||||||||
|
Tariff rate, RUB / h |
||||||||||
|
Labor remuneration system |
||||||||||
|
Schedule |
||||||||||
|
Continuation of table 13 |
||||||||||
|
The number of employees taking into account the substitution |
||||||||||
|
Planned implementation of production standards |
||||||||||
|
Working time fund, person / h |
||||||||||
|
Work on holidays |
||||||||||
|
Processing according to the schedule, person / hour |
||||||||||
|
Work at night, person / hour |
||||||||||
|
Work in the evening |
||||||||||
|
Basic salary, rubles / month (? Page 10.1? 10.8) |
||||||||||
|
Pay according to tariff (page 4 * page 9) |
||||||||||
|
Piecework break-in |
||||||||||
|
Manufacturing award |
||||||||||
|
Additional payment for work on holidays |
||||||||||
|
Supplement for processing on schedule |
||||||||||
|
Supplement for night work |
||||||||||
|
Supplement for work in the evening |
||||||||||
|
Surcharge according to the regional coefficient |
||||||||||
|
Additional salary |
||||||||||
|
Total wages per worker (p. 10 + p. 11) |
||||||||||
|
Total wages of all workers |
||||||||||
Explanations for Table 13:
Calculation of the fund of working time (clause 9):
tmonth= 365 * From shifts *tshifts/ (12 * b) (71)
where C shifts = 2 - the number of shifts per day,
t shifts = 12 hours - duration of one shift,
b = 4 - the number of brigades,
t month = 365 * 2 * 12 / (12 * 4) = 182.5 people * hour
Duration of work on holidays:
tNS= n pr * C shifts *tshifts/ (12 * b) (72)
t pr = 11 * 2 * 12/12 * 4 = 5.5 people * hour
Duration of processing according to the schedule:
T month = t gr - (2004/12),
t gr =? t month -t pr.
T month = 182.5-2004 / 12 = 15.5 people * hour,
t gr = 15.5-5.5 = 10 people * hour.
Calculation of working hours at night and in the evening:
t night = 1/3 * t month,
t eve = 1/3 * t month,
t night = 1/3 * 182.5 = 60.83 people * hour,
t evening = 1/3 * 182.5 = 60.83 people * hour.
Calculation of wages according to the tariff (clause 10.1):
Salary container = t hour * t month,
t hour - hourly tariff rate.
For the 7th category: salary tar = 24.78 * 182.5 = 4522.35 rubles;
For the 6th category: salary tar = 21.71 * 182.5 = 3962.07 rubles.
For the 5th category: salary tar = 18.87 * 182.5 = 3443.78 rubles;
Calculation of piecework extra work (clause 10.2):
ZP sd = ZP tar * [(N vyr -100) / 100], where
N exp is the planned fulfillment of production standards,%.
For both workers:? ZP sd = 0, since the output rate is 100% and there is no running-in.
Calculation of the production bonus (clause 10.3):
Salary premium = (ZP tar. +? ZP sd) * Bonus / 100%,
The size of the production bonus established in this area is 40%.
For the 7th category: salary premium. = (4522.35 + 0) * 40% / 100% = 1808.94 rubles;
For the 6th category: salary premium. = (3962.07 + 0) * 40% / 100% = 1584.83 rubles.
For the 5th category: salary premium. = (3443.78 + 0) * 40% / 100% = 1377.51 rubles;
Calculation of additional payments for work on holidays at a production rate of 100%:
ZP pr = t hour * (100/100) * t pr.
For the 7th category:? ZP pr = 24.78 * 5.5 = 136.29 rubles,
For the 6th category:? ZP pr = 21.71 * 5.5 = 119.41 rubles.
For the 5th category:? ZP pr = 18.87 * 5.5 = 103.78 rubles,
Calculation of additional payment for processing according to the schedule (37.5%):
ZP gr = t hour * (37.5 / 100) * t gr
For the 7th category:? ZP gr = 24.78 * 10 * 0.375 = 92.93 rubles,
For the 6th category:? ZP gr = 21.71 * 10 * 0.375 = 81.41 rubles.
For the 7th category:? ZP gr = 18.87 * 10 * 0.375 = 70.76 rubles,
Calculation of additional payments for work at night (40%):
ZP night = t hour * (40/100) * t night
For the 7th category:? ZP night = 24.78 * 0.4 * 60.83 = 602.95 rubles,
For the 6th category:? ZP night = 21.71 * 0.4 * 60.83 = 528.25 rubles.
For the 5th category:? ZP night = 18.87 * 0.4 * 60.83 = 459.14 rubles,
Calculation of additional payments for work in the evening (20%):
ЗП pm = t hour * (20/100) * t pm
For the 7th category:? ZP vech = 24.78 * 0.2 * 60.83 = 301.47 rubles,
For the 6th category:? ZP vech = 21.71 * 0.2 * 60.83 = 264.12 rubles.
For the 5th category:? ZP vech = 18.87 * 0.2 * 60.83 = 229.57 rubles,
The regional coefficient for the Ural region is 15%.
ZP p = 0.15 * (ZP tar +? ZP sd +? ZP pr +? ZP gr +? ZP night +? ZP vech + ZP prem.).
For the 7th category:? ZP p = 0.15 * (4522.35 + 0 + 1808.94 + 136.29 + 92.93 +
602.95 + 301.47) = 1502.32 rubles,
For the 6th category:? ZP p = 0.15 * (3962.07 + 0 + 1584.83 + 119.41 +
81.41 + 528.25 + 264.12) = 966.01 rubles.
For the 5th category:? ZP p = 0.15 * (3443.78 + 0 + 1377.51 + 103.78 + 70.76 +
459.14 + 229.57) = 852.68 rubles,
Calculation of additional wages (clause 11):
With the duration of the next vacation of 30 days, the coefficient of dependence of additional wages on the main one is 17.5%.
For the 7th category: salary extra = 0.175 * 8584.67 = 1502.32 rubles,
For the 6th category: salary extra = 0.175 * 7406.10 = 1296.07 rubles.
For the 5th category: salary extra = 0.175 * 6537.22 = 1144.01 rubles.
4.4 Calculation of social contributions
Annual payroll:
Payroll year =Snumber* Salary month * 12 (73)
where S number - payroll,
Salary month - monthly salary of one employee.
Payroll year = (80695.92 + 69617.36 + 30724.92 + 34808.68 + 30724.92) * 12 = 2958861.6 rubles
Table 14 - Calculation of contributions to extrabudgetary funds
Total payroll with deductions: 2958861.6 + 1053354.7 = 34012216.33 rubles.
4.5 Calculation of production costs
Table 15 - Calculation of the cost of 1 ton of finished products
|
Cost item name |
Price, rub / unit |
deviation |
||
|
1.semi-finished products, t |
||||
|
Ends and cutoffs into the charge Ends and cutoffs are substandard Scale |
||||
|
For rent Marriage 1st limit For metal |
||||
|
Total minus waste and rejects |
||||
|
1.electricity |
||||
|
2.technological fuel |
||||
|
3.waste heat |
||||
|
4.technical water |
||||
|
5.compressed air |
||||
|
8.supporting materials |
||||
|
9.basic salary of PR |
||||
|
10.additional salary of PR |
||||
|
11.deductions for social needs |
||||
|
12.amortization |
||||
|
13.replaceable equipment incl. rolls |
||||
|
14.transportation costs |
||||
|
Total costs for redistribution |
||||
|
15. losses from marriage |
||||
|
16. pickling costs |
||||
|
17.costs for heat treatment |
||||
|
Total production cost |
||||
Calculations for table 15:
1. Basic wages of production workers:
ZP main = ZP main * 12 *Snumber/ Qyear (74)
Salary main = (8584.67 * 8 + 7406.10 * 12 + 6537.22 * 8) * 12/187946 = 3.46 rubles.
2. Additional pay for production workers:
ZP add = ZP add * 12 *Snumber/ Qyear (75)
Salary add = (1502.32 * 8 + 1296.07 * 12 + 1144.01 * 8) * 12/187946 = 0.61 rubles.
3. Deductions from the wage fund:
Deductions from the wage bill were calculated in the previous chapter in table. 3 and amount to 2,958,861.6 rubles. for the entire annual volume of production, then for 1 ton they will be: 2958861.6 / 186946 = 4.07 rubles.
In the design version, all items of the calculation will remain unchanged, except for the costs of replacement equipment (rolls).
4.6 Calculation of the main technical and economic indicators
Profit from product sales:
Pr = (C-C / s) * Qyear (76)
where C is the average wholesale price excluding VAT for 1 ton of finished products.
P = 4460 rubles, then with VAT P = 5262.8 rubles.
- in the basic version:
Pr = (4460-4052.85) * 1002870 = 408318520 rubles,
- in the design version:
Pr / = (4460-4026.89) * 1002870 = 434353026 rubles.
Table 16 - Calculation of net profit
|
The name of indicators |
Amount, rub. |
Deviations |
||
|
Revenue from product sales, total (Price with VAT * Qyear) |
||||
|
incl. VAT (line 1 * 0.1525) |
||||
|
Revenue from product sales net of VAT (line 1 - line 2) |
||||
|
Production cost (С / с * Qyear) |
||||
|
Administrative expenses |
||||
|
Business expenses |
||||
|
Gross profit (lines 2-3-4-5) |
||||
|
Proceeds from the sale of fixed assets and other property |
||||
|
Interest receivable |
||||
|
Income from government securities |
||||
|
Income from participation in other organizations |
||||
|
Other non-operating income |
||||
|
Payments for the use of natural resources |
||||
|
Expenses for the sale of fixed assets and other property |
||||
|
Other operating expenses |
||||
|
Percentage to be paid |
||||
|
Property tax |
||||
|
Other non-operating expenses |
||||
|
Profit of the reporting year (? Page 6? 11 -? Page 12? 18) |
||||
|
Taxable Income (pp. 19-8-9-10) |
||||
|
Income tax (line 20 * 0.24) |
||||
|
Net income (line 19 - line 21) |
||||
PC = 326888666-307102442 = 19786224 rub.
Product profitability:
Pp = (Pr / S / s) * 100% (77)
- in the basic version:
Pp = (4460-4052.85) / 4052.85 * 100% = 10%,
- in the design version:
Pn / = (4460-4026.89) / 4026.89 * 100% = 10.75%.
PNP = Pch / I (78)
where And is the total investment.
The total investment is equal to the sum of capital costs (I = Kz = 6,480,000 rubles.)
PNP = 326888666/6480000 = 50.44.
Payback period:
Current = I /? PC (79)
Current = 6480000/19786224 = 0.32 g or 4 months.
Conclusion
It is proposed to replace the use of solid-forged backup rolls in 5.6 stands of mill 2500 (LPC-4) of OJSC MMK with composite rolls.
Based on the review, analysis of the designs and operating experience of the shrouded rolls, the optimal design of the composite roll was chosen in terms of the speed of its production and lower cost.
It is proposed to use 150KhNM or 35Kh5NMF steels as the material for the bandage, the wear resistance of which is 2-3 times higher than that of 9KhF steel, from which solid-forged rolls are made. The bandages are proposed to be made cast with triple normalization. Use used rolls for the production of axles.
Calculations were made of the stress-strain state and bearing capacity for various values of the landing diameters (? 1150 mm and? 1300 mm), the minimum, average and maximum values of the interference (D = 0.8; 1.15; 1.3) and the coefficient of friction ( f = 0.14; 0.3; 0.4). It was found that in the case of 1150 mm, the stress distribution pattern in the roll is more favorable than for 1300 mm, and the bearing capacity is 1.5-2 times higher. But with an increase in the tightness, the tensile stresses in the joint also increase, exceeding those allowed for steel 150KhNM. Therefore, it becomes advisable to use the minimum interference D = 0.8 mm, which ensures the transmission of torque with a sufficient margin even with a minimum friction coefficient f = 0.14.
To increase the bearing capacity of such a joint without increasing the stress values, it is proposed to increase the coefficient of friction on the mating surfaces by applying a metal coating. Aluminum was chosen as the coating material based on its cost and thermophysical properties. As the experience of using such a coating on the mating surfaces of the axle and the tire in the operating conditions of compound rolls on the mill 2000 (LPC-10) of OJSC MMK shows, aluminum increases the coefficient of friction to f = 0.3-0.4. In addition, the coating increases the area of actual contact between the axle and the tire and its thermal conductivity.
The maximum possible deflection, determined by calculation, is 0.62 mm, the slip zone is 45 mm.
The connection of the shroud with the axle is carried out in a thermal way, by heating the shroud to 350 ° -400 ° С.
Based on the calculations, the selected design of the composite roll with cylindrical seating surfaces of the axle and the tire, without the use of any additional fixing devices (collars, cones, keys), was found to be optimal.
To prevent fretting corrosion and relieve the concentration of residual stresses at the ends of the tire, bevels are made at the edges of the axis, so that in the zones adjacent to the ends of the tire, the interference is zero.
The cost of a composite roll is 60% of the cost of a new one-piece roll (1.8 million rubles). With the transition to composite rolls, their consumption will be reduced from 10 to 6 pieces per year. The expected economic effect will be about 20 million rubles.
List of sources used
- Helpful. Maud. 35606 RF, IPC В21В 27/02. Composite rolling roll / Morozov A.A., Takhautdinov R.S., Belevsky L.S. and others (RF) - No. 2003128756/20; declared September 30, 2003; publ. January 27, 2004. Bul. No. 3.
- Roll with sintered tungsten carbide metal rim. Kimura Hiroyuki. Japanese. patent. 7B 21B 2700. JP 3291143 B2 8155507A, 29.11.94.
- Helpful. Maud. 25857 RF, IPC В21В 27/02. Rolling roll / Wind V.V., Belkin G.A., Samoilov V.I. (RF) - No. 2002112624/20; declared 05/13/2002; publ. October 27, 2002. Bul. No. 30.
- Pat. 2173228 RF, IPC В21В 27/03. Rolling roll / Wind V.V., Belkin G.A. (RF) - No. 99126744/02; declared 12.22.99; publ. 10.09.01 //
- Pat. 2991648 RF, IPC В21В 27/03. Composite rolling roll / Poletskov P.P., Firkovich A.Yu., Tishin S.V. and others (RF) - No. 20011114313/02; declared May 24, 2001; publ. October 27, 2002. Bul. No. 30.
- Helpful. Maud. 12991 RF, IPC В21В 27/02. Composite roll / Poletskov P.P., Firkovich A.Yu., Antipenko A.I. and others (RF) - No. 99118942/20; declared 09/01/99; publ. 03/20/2000. Bul. No. 8.
- Pat. 2210445 RF, IPC В21В 27/03. Composite roll / Poletskov P.P., Firkovich A.Yu., Antipenko A.I. and others (RF) - No. 2000132306/02; declared 12.21.2000; publ. 20.08.2003. Bul. No. 23.
- Grechishchev E.S., Ilyaschenko A.A. Interference connections: Calculations, design, manufacturing - M .: Mashinostroenie, 1981 - 247 p., Ill.
- Orlov P.I. Basics of design: Reference and methodological manual. In 2 books. Book. 2. Ed. P.N. Uchaev. - 3rd ed., Revised. - M .: Mashinostroenie, 1988 .-- 544 p., Ill.
10 Narodetsky M.Z. To the choice of landings for rolling bearing rings. "Engineering Collection" Institute of Mechanics of the Academy of Sciences of the USSR, vol. 3, no. 2, 1947, p. 15-26
11 Kolbasin G.F. Investigation of the performance of composite rolling rolls with a replaceable tire: Dis .: ..kts. - Magnitogorsk, 1974 .-- 176 p.
12 Timoshenko S.P. Strength of materials, h. P.M. - L., Gostekhteorizdat, 1933.
13 Balatsky L.T. Fatigue of shafts in the joints. - Kiev: Technique, 1972, - 180 p.
14 Polukhin P.I., Nikolaev V.A., Polukhin V.P. and other Strength of rolling rolls. - Alma-Ata: Nauka, 1984 .-- 295 p.
15 Hot strip rolling on the 2500 mill. Technological instruction TI - 101-P-Ch. 4 - 71-97
16 Calculation of the multiplicity of using the axis of a composite roll / Firkovich A.Yu., Poletskov P.P., Solganin V.M. - Sat. Centre. lab. OJSC MMK: vol. 4. Magnitogorsk 2000. - 242 p.
17 Sokolov L.D., Grebenik V.M., Tylkin M.A. Research of rolling equipment, Metallurgy, 1964.
18 Sorokin V.G. Grade of steels and alloys, Mechanical Engineering, 1989.
19 Firsov V.T., Morozov B.A., Sofronov V.I. and others. Research of the operability of press connections of the shaft-sleeve type under conditions of static and cyclic alternating loading // Bulletin of mechanical engineering, - 1982. №11. - with. 29-33.
20 Safyan M.M. Rolling of broad-strip steel. Publishing house "Metallurgy", 1969, p. 460.
21 Tselikov A.I., Smirnov V.V. Rolling mills, Metallurgizdat, 1958.
22 Firsov V.T., Sofronov V.I., Morozov B.A. Experimental study of rigidity and residual deflection of shrouded backup rolls // Strength and reliability of metallurgical machines: Proceedings of VNIMETMASH. Sat. No. 61. - M., 1979 .-- p. 37-43
23 Bobrovnikov G.A. The strength of the landings carried out with the use of cold. - M .: Mashinostroenie, 1971. - 95 p.
24 Belevsky L.S. Plastic deformation of the surface layer and formation of the coating when applied with a flexible tool. - Magnitogorsk: Lyceum of the Russian Academy of Sciences, 1996 .-- 231 p.
25 Chertavskikh A.K. Friction and lubrication in metal forming. - M .: Matallurgizdat, 1949
26 Vorontsov N.M., Zhadan V.T., Shneerov B.Ya. and others. Operation of rolls of blooming and section rolling mills. - M .: Metallurgy, 1973 .-- 288 p.
27 Pokrovsky A.M., Peshkovtsev V.G., Zemskov A.A. Assessment of crack resistance of bandaged rolling rolls. Vestnik mashinostroeniya, 2003. No. 9 - p. 44-48.
28 Kovalev V.V. Financial Analysis: Methods and Procedures. - M .: Finance and statistics, 2002. - 560 p .: ill.
Introduction
rolling coiler multi-roll mill
At present, metallurgy occupies a special place in the industry of any country. Metallurgy is a field of science, technology and industry that encompasses the processes of obtaining metals from ores or other materials. By changing the chemical composition and structure, it is possible to obtain certain properties of the manufactured metal, as well as impart a certain shape and size.
One of the largest metallurgical plants in the Russian Federation is the Magnitogorsk Iron and Steel Works. His income is about 50 billion rubles. With such an income, a new stage in the development of the plant was the introduction of modern technological processes for the entire production.
Since 1992, MMK's main goal has been to modernize production and reach a modern technological level. What the plant had worked on before was not only morally obsolete, but also physically worn out. The first transformations were made in the era of the economic crisis, when the main consumers of the metal no longer supported the demand in Russia. During these difficult years, MMK entered the world ferrous metals market.
Since 1997, modernization has become the basis of a new industrial philosophy, a development strategy for the new century. The transformations affected absolutely all redistributions of the metallurgical complex: sintering, coke-chemical, blast-furnace production and the main steel-making site.
Today, the Magnitogorsk Iron and Steel Works is a high-quality steel of the brands required by the consumer and world-standard flat products for consumer goods from cars to household appliances.
Production of sheet metal has been developed predominantly.
In 1958, a resolution of the USSR Council of Ministers was adopted on the design and construction of the first stage of the 2500 mill complex for hot rolling of steel sheet. Before its construction, a large amount of preparatory work was carried out to release the site. 19.2 thousand square meters of temporary housing were demolished, a tram line and a road, three kilometers of underground communications, seven kilometers of railways, a warehouse for fuels and lubricants were moved. 1.38 million cubic meters of soil was cut for the site planning. The need to erect such a mill was dictated, first of all, by an acute shortage of steel billets for the production of large-diameter pipes in the country.
In September 1959, after the site was completely vacated, the construction of the mill foundation began.
The Economic Council of the Chelyabinsk Economic Administrative Region, by its resolution, approved measures to accelerate the construction and commissioning of the mill complex, which in its characteristics was not inferior to American, British, French and German counterparts.
Having finished the construction of the slabbing, the Magnitostroy trust, without hesitating for an hour, began the construction of a 2500 hot strip mill. The country was in dire need of a wide steel sheet, so the entire huge amount of work had to be done in a short time.
Immediately after launch in April 1959. slabbing - a billet mill for sheet mills - the construction of a hot rolling mill 2500 and all other units, which subsequently constitute a complex of sheet shop No. 4, began. The mill itself, embodying all the latest achievements of science and technology, was built in a record short time, eighteen months. On December 27, 1960, the state commission signed an act of acceptance into operation of the 2500 hot rolling steel sheet. This date is considered the birthday of LPC-4.
The design and supply of the main technological equipment was carried out by the Novokramatorsk Machine-Building Plant. Cutting unit - Starokramatorskiy. Special orders were carried out by the heavy machine building plants "Electrostal" and Alma-Ata. The weight of the processing equipment of the first stage of the mill was 21,500 tons.
Hot testing of the technology began a little earlier: December 20, 1960. brigade of the senior roller E.I. Tsvetaev under the guidance of the master Yu.Kh. Shaikhislamova rolled the first strip of steel sheet along the entire line of the 2500 mill. The official launch of the 2500 mill took place on December 27, 1960.
In honor of the significant date, a telegram from the Central Committee of the CPSU and the Council of Ministers was sent to Magnitka with congratulations on the early construction of the first stage of the continuous broadband mill "2500".
Currently, a significant part of our products is rolled stock for cold rolling. Some of the rolled products produced at Rolling Shop # 4 are exported. Export deliveries of metal products are important for the economies of Ukraine, Belarus and Kazakhstan.
Increasing requirements for the quality of finished rolled products lead to the need to introduce reliable and modern equipment into the technological process. As a result of the introduction of a new multi-roll coiler, it is possible to obtain a qualitatively new level of finished products. Also in the diploma project, a calculation was made of the economic efficiency of the introduction of a new multi-roll coiler on the 2500 mill.
1. General part
1.1 Requirements for hot rolled stock and raw materials
KKTs slabs (cast billet) are used as an initial billet for the 2500 mill.
Cast billet KKTs:
the chemical composition of the steel must meet the requirements of the relevant GOST or TU;
cast slabs must be cast in accordance with STP MMK-98-03 and cut to lengths in accordance with UPP orders;
the dimensions of the slabs and the limit deviations must comply with the requirements.
Table 1 - Slab dimensions and limit deviations
the convexity (concavity) of the edges should not exceed 10 mm per side; rhombicity (difference in diagonals) of the slab cross-section should not exceed 10 mm; the slant of the cut should not exceed 30 mm; crescent shape (curvature in width) of slabs should not be more than 10 mm per 1 m of length, non-flatness should not be more than 20 mm per 1 m; on the surface of slabs there should be no belts, sagging, captivity, cracks, bubbles, slag inclusions; traces of the reciprocating movement of the mold and snakes (splashes) without accompanying cracks are not a rejection sign; slabs made of low-carbon high-quality, high-quality carbon structural and ordinary steel with a carbon content of up to 0.23%, having an "axial crack" defect with a continuous length of more than 600 mm, extending at a distance of no closer than 150 mm to a narrow edge and having an opening width of no more than 1 mm, are allowed for further processing in cold rolling shops. slabs must be clearly marked with the following content: the number of the heat, strand and the serial number of the slab. Sometimes there is a duplicate marking of the melt number on the ends of the slabs; slabs are handed over and accepted by theoretical weight. 1.2 Product quality control
Permissible deviations in thickness, width, requirements for the surface of rolled strips in coils must comply with GOST 19903-74, GOST 5521-93, GOST 19281-89, GOST 14637-89, GOST 16523-97, GOST 1577-93, GOST 4041-71 , technical conditions and STP 14-101-81-97 and STP 14-101-65-96 for hot-rolled strips in coils for LPC-5 and LPC-8. On the strip, pits and pores are not allowed, which are observed on the surface after descaling. Pits and pores on hot rolled steel strip and thin sheet are not removed for technical and economic reasons. A defect such as bubbles on the strip is also undesirable. A hot-rolled strip affected by bubbles is unsuitable for further cold rolling. The rolls should be tightly wound and should not have loose ends; the outer end of the strip should fit well with the rest of the rolls. On the edges of the turns of the rolls there should be no twists, dents, adhesions and flaws that go beyond half the width tolerances in accordance with the requirements of GOST. On the surface of the strip, there should be no rolled scale, furnace slag, depressions from the coiler rollers and mill rolls, detectable with the naked eye. The telescopicity of the rolls should be no more than: for strips with a thickness of 2.0-2.5 mm - 75 mm; for strips over 2.5 mm thick - 50 mm. The rolls must be cylindrical. 1.3 Main and auxiliary equipment of the workshop
The mill consists of the following sections: Heating furnaces area; The actual mill with coilers. Heating furnaces area: The equipment for the heating furnaces section includes: lifting tables; Slab pusher; roller conveyor in front of the ovens; double pusher; feed roller conveyor; oven buffers; heating furnaces. Lift tables are installed at the loading roller tables in front of the furnaces, they are used to receive slabs and to feed them one by one to the roller conveyor using a pusher. Slab pusher is designed to feed slabs from a lifting table to a roller conveyor. Pushing is carried out by rack and pinion rods connected by a pushing traverse. The rods are moved by right and left mechanisms with a common drive. The double pusher is used to feed the slabs of the loading roller table into the double-row heating furnace and move them through the furnace until they are dispensed onto the receiving roller table. The feed roller table is designed to receive slabs falling out of the furnace and transport them to the working stands of the mill. The roller table in front of the furnaces is located on the front side of the heating furnaces and is designed to feed slabs to the furnaces. If necessary, slabs can be fed to the furnaces via a roller table directly from the slab harvesting devices. The roller conveyor in front of the furnaces consists of 19 sections of the same type with a group drive. The buffers at the kiln are designed to extinguish the impact energy of the slabs pushed along the inclined beams from the kiln. Buffers consist of a plate, bed, springs. The buffers have 4 cars each, on which coil springs are located to absorb the slab impact. Buffer plates with inclined front plane for better absorption of impact energy.
Heating furnaces are designed to heat up slabs before rolling. Methodical furnaces are equipped with recording devices and automatic regulators, i.e. automatic control devices. Methodical furnaces operate on evaporative cooling with forced circulation. It is possible to switch the unit from evaporative cooling to service water. The method for descaling the zones is by hand scraping. To transport scale and slag from the furnaces to the sludge tunnel, a hydraulic flush system is used, located between the furnaces. Figure 1 - Roller with individual drive Station span. Continuous hot-rolling "2500" thin-sheet mill consists of roughing and finishing groups of stands. The draft group includes: reversible duo stand; widening cage quarto; reversible quarto stand; universal quarto stand. The finishing group includes: finishing scale breaker - "duo" stand; 7 finishing stands "quarto" In front of the finishing scaler, 35 mm flying shears are installed to trim the front and rear ends of the roll. Feeding rollers; 2- drums with scissors; 3- knives; Roller table rollers; 5- strip Figure 2- Scheme of double-drum flying shears The roughing stands are universal, i.e. in addition to horizontal rolls, there are vertical rolls designed for crimping the side edges of slabs. Vertical rolls are located at the front of the stands. The roller tables in front of each working stand are equipped with rack-and-pinion guide rails, which are adjusted depending on the width of the rolled strip and ensure its correct entry into the rolls. The roller conveyor in front of the flying shears is equipped with the same rulers. After cutting the front end, the rolled stock is rolled in a finishing mill and 7 finishing stands "quarto". Between the shears and the finishing scaler there are rack-and-pinion rulers and four individually driven rollers. Between a pair of finishing stands there are guides and loopers with a lever lifting drive from an electric motor. Lower and upper overhead guides are installed behind the finishing mill and behind each finishing stand. The system of guides, loop holders and guide lines ensures the correct passage of the rolled strip. Overhead guides also protect the strip from water cooling the rolls. The roller conveyor sections located directly at the coilers have movable ruler guides with screw and pneumatic drives. The rulers are activated by a pneumatic drive after each run of the strip into the corresponding coiler and contribute to obtaining a high-quality coil winding without telescopicity. The stands of the closed stands with I-beams are made of cast steel. Work rolls - steel and cast iron. Back-up rolls are forged steel. Work roll bearings: double row with tapered rollers, back-up roll bearings - fluid friction. Pressure mechanism - with globoid gearboxes for each screw. The mechanism for balancing the upper backup roll is hydraulic with an upper cylinder. A bronze nut of a pressure screw is pressed into the upper cross member of each bed. Grease is supplied to the thread of the pressure screw through the holes in the nut. For the convenience of roll transfer, the width of the frame windows on the transfer side is 10 mm larger than on the drive side. The work roll chocks and the corresponding back-up roll chocks are lined with replaceable strips. For a stable position of the work rolls during rolling, their axes are located at a distance of 10 mm along the metal path relative to the axis of the backup rolls. The work roll chocks are attached to the back-up roll chocks with latches on the transfer side. On the drive side, the chocks of the work rolls are fixed, which allows axial displacement of the chocks as the rolls lengthen from thermal expansion. Back-up rolls are fixed in the stand against axial movement by fixing the chocks from the transshipment side to the beds of the kerchiefs. On the drive side, the back-up roll chocks are also not fixed. Figure 3- Group of continuous stands of hot rolling mill 2500 The electric motors of the pressing device of the roughing stands and the scaling mill are interconnected by a friction clutch and an electromagnetic uncoupling drive. This clutch allows for joint and separate activation of the push mechanism motors. There are no electromagnetic clutches on the pressing devices of the finishing stands. Synchronous rotation of the left and right thrust screws is ensured by the synchronization circuitry. The drive power of the pressure mechanism is sufficient to tighten the screws during rolling while passing the metal in the rolls. The limitation of the lifting of the pressure screws in the upper position is carried out by the command devices. To indicate the position of the screws on the control panel, an agricultural sensor is connected to each pressing device through a spur gearbox. Mill roll hydraulic balancing system. The system serves to balance the upper work and back-up rolls and press firmly against the pressure screws. The balancing system of the roughing group includes: pumping station in oil basement No. 2; two cargo batteries; two hydraulic accumulators; piping system; working cylinders; oil dispensers. The balancing system of the finishing rolls includes: pumping station in oil basement No. 3; one cargo battery. Hydraulic system of mechanisms for changing rolls and latches of 5-11 stands, reversing stands for duo and quarto. The system is designed for: drive of cylinders of mechanisms for changing back-up and work rolls of finishing stands No. 5-11; drive of pneumatic cylinders of coupling mechanisms when changing back-up rolls of stands No. 5-11; drive of hydraulic cylinders of latches for fastening rolls of roughing and finishing mill stands. The hydraulic system consists of a pumping station located in the roll transfer pumping station, manual slide switches, and control valves. Strip cooling system on the discharge roller table. To ensure the technological temperatures of strip coiling, a system of artificial (accelerated) cooling with water from above and from below using a sprinkler system is provided on the mill. The strip cooling system on the outlet roller table of a 2500 gp mill is designed for forced cooling of hot-rolled strips in order to maintain the hot-rolled strip coiling temperature set by the technology, as well as to ensure the homogeneity of the microstructure and mechanical properties along the length of the strip of the entire range of the mill. The equipment includes: water filtration unit; strip cooling system; pneumatic control system; water breakdown system; hydraulic control system for lifting sections; hydroelectric station 10 MPa; installation of a LAND pyrometer. To ensure the strip cooling modes required by the technology and to maintain the strip temperature before coiling on the corresponding coiler, the strip cooling system is combined and is conventionally divided into three sections: section No. 1 consists of six upper and six lower cooling sections. Water consumption for each section is adjustable. The section is designed for accelerated and monotonic cooling of strips; section No. 2 consists of 24 upper and 24 lower cooling sections. Water consumption for each section is not regulated. The section is intended only for monotonous strip cooling; section No. 3 of "thin" cooling, consists of eight upper and eight lower cooling sections. Water consumption for each section is adjustable. The section is intended for the implementation of the modes of late and monotonic cooling of the strips. The equipment of this section is also used for "fine" final cooling mode and for temperature control during automatic operation. The cooling system consists of: 38 controlled sections of top cooling; 38 controlled bottom cooling sections. One top cooling section includes: on site No. 1 - one slotted tank with a slot size of 10 × 2500 mm; at site No. 2 - two tanks with siphons made of pipes DN 25 mm; on site No. 3 - one slotted tank with a slot size of 8´2500 mm. One bottom cooling section includes: in sections # 1 and # 3 - four collectors with flat-spray nozzles; at site No. 2 - five collectors with flat-spray nozzles. The combination of switching on the required number of upper and lower cooling sections, as well as by presetting the required water flow through the lower and upper cooling sections in sections 1 and 3, provides the strip cooling mode required by the technology and the set winding temperature. When the strip passes along the roller table, the required number of upper and lower cooling sections is switched on. In this case, the option of separate switching on of the upper and lower sections is possible. When rolling with acceleration, additional sections can be connected. In the automatic mode of the cooling system, the controlled sections are switched on and off automatically as the front and rear ends of the strip approach and leave from under the working cooling sections. This mode also provides for the possibility of rolling without cooling the front and rear ends of strips about 10-15 m long. The strip cooling system provides for the possibility of controlling the cooling process in manual, semi-automatic and automatic modes, from the control station of the finishing group of stands. In order to increase the cooling capacity, 24 pieces are installed along the entire system. installations for water removal of waste water from the upper surface of the strip with water of high pressure P = 0.8-1.0 MPa. Water stripping units are provided after every two slotted or four tanks with top cooling siphons. During normal mill operation, the upper cooling sections should be lowered. The lifting of the upper cooling sections is carried out by hydraulic cylinders when servicing and replacing equipment elements of the discharge roller table, as well as when drilling the strip. Each two sections of the upper cooling are mounted on their own supporting rotary frame, the lifting and lowering of which is provided by a double-acting hydraulic cylinder. The control of the hydraulic cylinders for lifting the upper sections is provided by four hydraulic control panels (GPU). Each hydraulic control panel has shut-off and control valves and five hydraulic valves. All hydraulic control panels are powered from an autonomous hydroelectric station P = 10 MPa, the equipment of which includes: oil tank with a capacity of 2 m 3; two pumping units NPl 80/16; filters for cleaning the working fluid; hydraulic units of safety and instrumentation; electrical control cabinet. All equipment of the hydroelectric station is mounted on a single frame. Cooling of the rolls of the roughing and finishing groups of the 2500 mill. The water supply for cooling the rolls of the 2500 mill is carried out from the pumping station No. 23. Technical water. The diameter of the water conduit is 1000 mm. For each stand from the water conduit, there is a wiring through pipes with a diameter of 325 mm. The finishing stands are equipped with valves for each stand. After the valves, there are three-way valves for supplying water to the rolls cooling headers, cooling the wiring of the stands and discharging water under the mill during its shutdown. Water descaling system in the mill. To clean the strip surface from scale formed both during heating of slabs in furnaces and during rolling in a mill, 5 water descaling units were installed. For descaling, industrial water is used, which is supplied by 5 high-pressure pumps. .4 Technological process for the production of hot-rolled sheet
The appointment of metal for rolling is carried out in accordance with the orders of the production department of the workshop and the schedule-task of the production department. Based on the rolling schedule, the slab warehouse foreman carries out a float supply of slabs to the loading roller table according to the schedule positions. The planting of metal in the furnace is carried out under the direct supervision of the plantor. Before embarkation, the operator enters information into the computer at the control station PU No. 2 with the indication of the heat number, steel grade, number and size of slabs, total weight of the heat and distribution of the number of slabs over the furnaces. The distribution of the melted slabs between all operating furnaces must be uniform. In the event of a computer failure, each melt put into the furnace is recorded by the fitter in the landing tag indicating the melt number, steel grade, purpose, size and number of slabs. The label, after filling, is transferred to the replaceable stacker-stacker for the delivery of metal from the furnaces. Before planting the metal in the furnace, the metal planter must remove slag and other foreign objects from the surface of the slabs. Final cleaning of slabs is carried out by blowing off scale with a jet of air under pressure from 2 nozzles located in front of furnaces No. 1 and No. 4. When the slabs of each new melt are planted, the operator puts a fireclay brick break on the tail section of the first slab and determines the dimensions of the first three slabs. If the measured values deviate from the requirements of TU 14-1-5357-98 and STP MMK 98-2003, the landing is terminated and the shift supervisor is notified. The metal planter and heaters constantly monitor the correct positioning of the slabs in the furnace through the loading window and viewing windows. Those slabs from which the sample is taken are set in the furnace in such a way that the section of the slab with the sample corresponds to the tail of the strip. If the slabs are inserted incorrectly into the furnace (tilting of slabs in the furnace, displacement of slabs in one direction as they move through the furnace, etc.), further slabs are immediately stopped and measures are taken to eliminate the malfunctions. When the metal is planted in the furnace, breaking and mixing of heats are not allowed. If there is a mixing of heats, slab sizes, stop dispensing slabs from the furnaces and notify the shift supervisor. When knocking out the smoky flame from under the dampers of the loading window, the operator of the control unit # 2 stops planting the metal and informs the heaters. The replaceable stacker-stacker according to the computer (landing tag) transmits information about the rolled metal through the ACS system with the indication of the melt-batch number, steel grade, slab sizes, strip sizes, weight of one strip of each size and total batch weight, purpose, standard or technical conditions ... The delivery of slabs for rolling is carried out strictly by float in accordance with the schedule-task, the order of planting and the required heating time. When the dimensions of the slabs or the dimensions of the rolled strip change, the stacker-operator announces the restructuring of the mill at the delivery through the loudspeaker line of the mill. Responsible for the correct delivery of slabs from the furnaces are the senior heater, metal heaters and the stacker-stacker at the delivery of the furnaces. In the event of a delay in one of the furnaces, the part of the melt located in the other furnaces is fully dispensed, after which rolling stops and measures are taken to eliminate the malfunctions. The temperature regime of the furnaces should ensure, during the technological course of rolling, the maximum temperature difference between the strips of one batch of 30 ° C. It is prohibited to dispense cold slabs or slabs with a lateral edge cooled down during mill stops. The senior heater and heaters are responsible for dispensing such slabs. If the lateral edge is getting cold, the slab should be assigned to discharge. The heated slabs are discharged from the furnace and fed to the duo stand via the outfeed roller table. In the rough scale mill, the relative reduction is 6-8%. After leaving the stand, the duo roll is fed into an extension stand and transported along a roller table for rolling in roughing stands. Rolling in duo and quarto stands can be carried out with reverse. The roll from the roughing group goes to the flying shears "35x2350" for cutting the front and rear ends of the strip. The front ends of the rolls are cut off on all metal, the rear ends of the rolls are cut off on metal no more than 4 mm thick and on the rest of the metal if the ends of the rolls have a larger tongue. Trimming of the ends of the roll is carried out in automatic mode. The ends of the rolls are trimmed to full width. Cut ends with a width of up to 150 mm are considered to be technological cuttings. The size of the cut end is set by the operator of the PU No. 5 gap according to the dial. From the flying shears "35x2350", the rolled stock enters the finishing group, where the strip being rolled is simultaneously in several stands. When distributing reductions in the stands, senior rolling makers monitor the loads on the motors of the main drives, which should not exceed the maximum permissible. The speed of rolling in the stands of the finishing group should ensure, under the conditions of the given values of reductions, the required temperatures of the end of rolling for a given profile and a given group of steel grades. To ensure the necessary mechanical properties of the metal, the strips are cooled with water before coiling into coils using a spray system located on the discharge roller table behind the finishing group of stands. The strips are subjected to cooling, depending on the steel grade and purpose, according to the appropriate modes. All strips rolled on the mill are coiled into coils on 4 coilers, after which they are transferred along the conveyors of hot-rolled coils to the roll storage of the hot or cold-rolled shops. On the mill line - before and behind the duo stand, behind the reversing stand, quarto and finishing mill, high-pressure water breakers are installed, with the help of which it is produced, knocking down scale from the metal surface. The operation of the water breakers must ensure the surface quality required by GOST. The water pressure during the simultaneous operation of all collectors must be at least 80 atm. (8 MPa). The amount of mechanical suspension in water should not exceed 20 mlg / l. The shop power engineer responsible for water quality control, who weekly asks the power shop for a certificate on water quality. Figure 4- Finishing work stand of a quarto continuous broadband mill 2500 The senior roller of the roughing group is responsible for the high-quality descaling at the water descaling behind the reversing duo and quarto stands, and the senior roller of the finishing group for the water descaling in the finishing scale mill. During the shift, the quality of the sheet is monitored for the presence of dross. If scale is found, the water descaling nozzles are inspected and cleaned by the shift personnel. Inspection and cleaning of the nozzles with a roughing group water stripping should be carried out on a daily basis for preventive maintenance. Inspection and cleaning of the 5th hydraulic breaker nozzles to carry out each reloading of the working rolls of the finishing group. Metal rolling should be carried out only with all hydraulic breakers working. In emergency situations, the roll in front of the finishing group collides into a "pocket" for under-rolls, is marked by the roughing group roller and, after cutting to measured lengths, is stored in a bag. Responsibility for observing the temperature regime of rolling rests with the senior rollers of the roughing and finishing groups, senior heaters. The temperature of the strip outside the 3 stand, the temperature of the end of rolling and the temperature of the strip coiling must correspond to the technological map. The required temperature of the end of rolling is achieved by changing the rolling speed in the finishing group, the thickness of the rolled stock within the limits of permissible loads, by switching on inter-stand cooling in the finishing group with a fixed rolling option. To control the dimensions of the rolled strips and the temperature regime of rolling, the following are installed on the mill line: strip width gauge behind 11 stand; X-ray thickness gauges behind 11 stands; pyrometers behind the 3rd stand, behind the 11th stand, between the second and third sections of the spray installation and in front of the coilers (above). If the strip dimensions deviate from the specified ones, the reductions in the stands are adjusted at the direction of the senior rollers. When a variable width and thickness of the strip is detected along its length, the strip tension is adjusted in the finishing stands, the strip acceleration mode is used. In the process of metal rolling, a significant amount of scale and technological scrap is formed. After being knocked down from the surface of the strips, the scale is washed off by service water through a sludge tunnel into special sedimentation tanks located in the scrap span of the mill. After settling, the scale is loaded with a grab crane into a railway or road transport and taken out of the workshop. The scrap metal obtained after flying shears is transported in special boxes to the scrap bay and shipped to special wagons for the needs of the steelmaking industry. Technological scrap, obtained on coilers, is cut by gas cutters to certain sizes, magnetically stored in boxes and shipped to special wagons for the needs of the steelmaking industry. Responsibility for timely cleaning, shipment of scale and technological trimmings rests with shift foremen of production, senior rollers and seniors at the coiler section. The coiler is designed for coiling strips rolled at a temperature not lower than 450 0 C. The coilers of a hot rolling mill must ensure high-quality and efficient coiling of strips into coils. The strip is captured by the coiler at a filling speed of up to 8 m / s, after which all mechanisms (finishing group, take-off roller table and coiler) are synchronously accelerated to a given rolling speed. The winding speed of the strip by the coiler, depending on the rolling speed, can be set automatically manually by the operator using a regulator. The operator only controls the speed of the pull rolls, which is set 2-5% higher than the speed of the last finishing stand. If at the specified ratio of speeds, the formation of a loop of the strip takes place, it is allowed to increase the speed of the pull rollers by 10% in relation to the rolling speed. The tension of the strip during coiling is adjusted by the operator using the tension regulator, which is indirectly determined by the strength of the motor current. Winding strips with a thickness of 2-10 mm from steel grades 35, 40, 45, 50 and 65G is carried out at tensions 1.5 times higher than the above. Coiling of strips on the mill is carried out on a group of coilers, and for the next 4 and 5, it is recommended to coil strips up to 4 mm thick, on coilers No. 7, 8 - over 4 mm. The coiler is ready to receive the strip, when the drum is unclenched, the stripping trolley is set to its original position, the forming rollers are brought together, the pulling roller is lowered, the wiring is raised, the rulers are pulled apart, the drum and forming rollers are rotating, water is supplied to all cooled elements of the coilers. The winder works in the following sequence: the band is set and the rulers are reduced; after winding 3-4 turns on the drum, the pressure of the rollers on the strip decreases; after the end of winding, the rulers are pulled apart, the drum and forming rollers stop, the upper pull roller rises, the wiring is lowered; forming rollers are bred; the drum is compressed; using a cart, the roll is removed from the drum to the turner; the cart returns to its original position, the roll is turned over onto the receiving cart and taken to the conveyor; the tilter goes to its original position; the drum is unclenched; forming rollers are reduced; the drum and forming rollers are accelerated; the pull roller is lowered and the harness is raised. Coilers No.4 and No.5 are equipped with automatic vertical strapping machines for strapping rolls with packing tape measuring 32 x 0.8 - 1.0 mm with 6 notches immediately after removing the roll from the reel drum. All coils of strips with a thickness of 1.8-3.0 mm (inclusive), wound on coilers No. 4 and No. 5, must be packed. In cases where a roll is removed from these coilers for sampling or for processing due to defects in winding, then do not strap these coils after winding, but tie them after sampling (or processing) with packing tape using a manual packaging machine. .5 Introduction of a new multi-roll coiler
It is planned to install a new hydraulic underground multi-roller in the shop. It will be necessary in order to ensure the winding of strips from higher-strength steels, as well as to meet the quality requirements and to ensure the necessary parameters of the coil, in particular, low telescopicity, high tension, and reduction of strip head marks on the initial turns. The new coiler includes a pinch roller control with separate motors; drive mechanism; hydraulic equipment; lubrication system; automation systems. It is also equipped with step control and larger motors. The roll diameter has been increased from 1900 to 2000 mm, the maximum winding speed is 18 m / s, the winding temperature is 300 - 900 0 C. A more powerful drive allows wind the strip with a tension of 60 kN. The mandrel is driven by a 1500 kW main drive connected to a gearbox with two gear stages. The pull rollers are driven by two 450 kW drives each. Thus, the power of the motors is approximately 7 times greater than that of the previous coiler. Since the mass, diameter and width of the coils became larger, the tilters were equipped with two high-pressure hydraulic drives capable of moving loads up to 15 tons. In addition, it is planned to install the Coil Master PL automation system for the coiler, which coordinates the coiler and calculates all installations according to the specification of the incoming strip. The shop will also receive a global data logging system that continuously records up to 300 signals from the coiler. Now diagnostics and fine tuning of the winder unit can be performed from any company PC or modem from home. The main functions of the system are: operational analysis of registered signals; check of all Win-CC displays including alarm logging. The existing visualization system (human-machine interface) will be replaced, and about 30 computer graphic displays will be introduced to provide a clearer overview of the coiler parameters and therefore better control of its operation. In addition, 70 computer graphic displays are installed showing the current values of settings and parameters. 1- bed, 2- reel drum, Swivel support, 4-roll remover. Picture 5 - Coiler with a gearless drive mill 2500 hot rolling mill 2500 First of all, a high pressure hydraulic system was installed. A control system with four hydraulic axles was used for the tilters. The installation and commissioning of the new equipment is scheduled to take place in just three weeks. The main feature of the coiler is that winding is done with open side guides in front of the pull roller. Increasing the power of the coiler drives and pulling rollers allows the winding of a strip with a tensile strength of up to 1000 N / mm 2. The telescopic properties of the bales have been greatly improved as a result of the high tension, the quality of the winding is due to the device for adjusting the pull rollers, which can work in two modes: force regulation (normal mode) and gap regulation (new technological mode). In addition, the use of a device for stepwise regulation of the gap (new technological mode). In addition, the use of a step regulation device makes it possible to avoid the appearance of scratches on the initial turns of the roll. This results in improved strip quality and production rates. Two existing bale tilters, as well as pull rollers and rollers for coiling the strip, equipped with a new hydraulic system with a pressure of 29 MPa, so even 15 t bales are now reliably transported. Thanks to the new underfloor multi-roll coiler, it has become possible to wind strips in a wide range of sizes and from high-strength steels. As a result, the plant achieved an expansion of the range of products. 1.6 Conclusion
In this diploma project, calculations were made of the reduction mode, power parameters, hourly productivity and economic efficiency of the introduction of a new multi-roll coiler on a 2500 mill. Thanks to the new underfloor multi-roll coiler, installed on the mill, it is possible to wind strips in a wide range of sizes and from high-strength steels. As a result, the mill achieved an expansion of the range of products. 2. Special part .1 Calculation of the reduction mode
Calculation of the reduction mode on a 2500 mill for a sheet with a thickness of 4.8 mm from a slab of 180 1050 4000 mm. Rough scale breaker. According to practical data in a rough scale mill, then Expansion cage: Roughing group of stands. Applied values of relative height reductions in the first stand 28.5%, and in the last 40%. First roughing stand (quarto). Accepted value then Knowing the extreme values, we build a graph. Figure 6- Schedule of the roughing group of stands Second roughing universal stand. According to the schedule, then Third universal roughing stand. Accepted then Fine descaler. We accept it in a finishing mill, then a strip with a thickness of mm will be set in the first stand, and a strip with a thickness of mm will come out of the last stand. Finishing group of stands. Determine the coefficient of vertical deformation (total and average). then, A strip 33 mm thick will leave the first stand if it is equal to 1.37 in all stands and Based on the practical data of the mill, that is 1.27 times more. Consequently, it should be as many times less, i.e. Having extreme values, we build a graph for the finishing group. Figure 7 - Graph of the finishing group of stands A strip of mm should come out of the seventh stand, therefore mm .2 Calculation of power parameters of the mill
Determine the force during hot rolling if the following initial data are known: rolls D = 710mm, roll speed = 250 rpm. Rolled metal - steel 08KP. The temperature of the metal during rolling is 1000 ° C. Absolute compression: Length of the contact surface of the deformation zone: Average height and width: Contact surface area: Rolling speed: where the roll diameter, D must be converted from millimeters to meters, i.e. D = 700mm = 0.70m The rolling force is determined by the method of A.I. Tselikova. Deformation rate: For a metal temperature of 1000 С 0 and the rate of deformation, the resistance to deformation is determined from the experimental curves kgf / Friction coefficient: where is the coefficient taking into account the material of the rolls for steel = 1.0 The coefficient taking into account the influence of the peripheral speed of the rolls is determined according to the graph Coefficient taking into account the influence of the chemical composition of the rolled steel Rolled metal temperature, С 0 Factor taking into account the effect of bandwidth: Where the coefficient is determined depending on the ratio if, then = 1.15 The coefficient is determined by the formula: For values = 3.8 and = 0.43, according to the graphs, = 1.64 The coefficient taking into account the influence of external zones is determined from the ratio. There is no rolling tension, therefore = 1.0, then the coefficient Contact pressure: Rolling force: Determine the rolling torque for a constant speed mill. Roll barrel diameter D = 710mm, roll speed = 250 rpm. Rolling force P = 1034 tf The length of the deformation zone: Rolling moment. Since in the last stand the strip has a rectangular cross-section, we take the shoulder coefficient = 0.5. Frictional moment in roll bearings. For textolite bearings, the coefficient of friction = 0.003 The moment required to carry out deformation in a given stand: Power required for deformation in a given stand: Let's take the power consumption at idle 8% of the nominal: kW (26) Let us determine the calculated power, taking into account the friction losses in the gears and idling: we take the efficiency of the spindles and couplings = 0.97, the efficiency of the gear stand = 0.93, the efficiency of the gearbox = 0.93. Overall efficiency: then: Rolling power = 5040 kW. .3 Calculation of hourly productivity of mill 2500
The hourly productivity of the rolling mill, A t / h, is determined by the formula: where, is the mass of the workpiece; Rolling rhythm. To determine the rolling mode, it is necessary to find the maximum time and pause time, s. where, is the length of the metal after the passage, m / s; Rolling speed, m / s. Now I find machine time Now I find the pause time for each pass using the formula: where, is the distance between stands, m; Now I find the rolling mode for the roughing group: I calculate the pause time and machine time for the finishing continuous group: where, is the length after rolling, m Travel speed along the intermediate roller table, m / s where, is the distance between the roughing and finishing groups, m The mass of rolled metal, t, is determined by the formula: where, is the specific gravity; Figure 8 - Graph of hourly productivity of broadband mill 2500 2.4 Computer version of the calculation of power parameters Calculation method The Donnichermet program was developed by the Donnichermet Institute for a 2000 hot rolling mill under construction and a 2500 hot rolling mill under reconstruction at OJSC MMK. Konovalova, A.L. Ostapenko, V.G. Ponomareva. Calculation of sheet rolling parameters, reference book Moscow, "Metallurgy" 1986. In this program, the calculation of the energy-power and temperature-speed conditions of rolling (at several points along the length of the roll and strip) is carried out only for a stand with horizontal rolls (it is likely that by that time the program for reduction, the slab in vertical rolls was not ready yet). Calculation of reduction modes for horizontal rolls of roughing stands. The calculation of the reduction modes in the mill stands is carried out taking into account the permissible angle, gripping, uniform loading of the roughing stands drive and the optimal loading of the finishing stands drive, the permissible values of rolling force P, moment M and rolling power N. According to experimental data. Polugikina V.P. we take the permissible nip angle for steel rolls = 17.5 ° for cast iron rolls = 16 ° The maximum compression is determined by the formula: Δh max D p (1-cos) = R p / 3316 mm. (40) The resulting calculated values are summarized in Table 1. Table 2 - Allowable reductions Δh by the angle of capture of metal by rolls
Parameter Stand numbers steel cast iron cast iron R, max / min Δh, max / min For the developed types of reduction regimes providing for a uniform distribution of loads over the roughing stands during the reduction of a slab with a thickness of 250 mm (in a heated state of 254 mm) onto rolling stocks with a thickness of 25-50 mm, a dependence was obtained to determine the absolute reduction along the stands: Δh j = (254-h n) mm, (41) where h n is the thickness of the roll, mm; The proportionality coefficient adopted for the stands according to the following data: Data
According to the calculated values of Δh, by the stands, a complete table of reduction modes is compiled, which is supplemented by the speeds of the rolls in free-standing stands No. 1-3 and the adopted speed in stand No. 6-depending on the thickness of the rolled stock: The rolling speed (or the output speed of the rolled stock) in these stands will be, taking into account a 5% lead, greater than the linear speed of the rolls: V = 1.05 V in, m / s. (42) Rolling speeds in stands N "4 and 5, as well as in vertical rolls, are determined from the constant of continuous rolling: V G j = V G6 h G6 / h j and V B j = V G j h j / H j, m / s. (43) The thickness of the rolling stock for the finishing group is torn out in such a way as to ensure uniform loading between the roughing and finishing groups of stands: Table 3
We develop typical rolling modes for a constant thickness of a cast slab of 250 mm (in a heated state 254 mm) for rolling stock with a thickness of 25-50 mm, excluding slab width and steel grade. On slabs with a width of 1850 mm, the loading of the roughing and finishing groups of stands will be maximum, and with a slab width of 750 mm, it will be minimal. When calculating Δh j, round the stands, they are rounded to whole values so that their sum is equal to (254-h n), mm. For example, Table 3 shows the design mode of rolling for a roll-up of 32 mm. Table 4 - Design mode of rolling in roughing stands for rolling h n = 32.
Rolling parameters Stand numbers The calculation program should also include manual reductions in the roughing stands. Let's define the reduction along the stands, if stand No. 3 will not work: Δh j new = Δh j (1 + 0.2013). (44) We get new reductions in the stands, taking into account rounding: 60 + 0 + 53 + 28 + 17 = 222 mm. According to these reductions, it can be seen that in stand No. 2 the natural capture of the metal by the rolls will not be ensured (see Table 3). Rolling is possible only for a tackle of at least 38-40 mm. After adjusting the compressions, we make a verification calculation on a computer and compare the obtained values of the energy-power parameters with the permissible values of P, M and N rolling for the 2000 mill of OJSC MMK. After rolling in vertical rolls, nodules are formed on the strip near the side edges, which increase the rolling force in subsequent horizontal rolls up to 10%. To calculate the reduced roll thickness, we will use the formula of Donnyichermet employees, suitable for taking into account the previous rolling in calibrated or smooth vertical rolls: H pr = H 0 B 0 / B 1 1/1 + ΔB / B 0 0.3 (B 0 / H 0) -0.05 (1 + 0.1 H c / B cr -B cd / 1-2H k / B 0) 0.33 (45) where H to - the depth of the box gauge, mm; In cr, V cd - the width of the caliber along the bottom and at the connector, mm. When rolling in smooth vertical rolls (H k = 0), the factor to the power of 0.33 will be equal to 1.0. when rolling in grooved rolls, it is always greater than 1.0. With a sequential calculation along the passes, it will always have H pr> H 0 and hence the actual reductions in horizontal rolls should be calculated using the formulas Δh Ф = H pr -h and E ph = Δh ph / H pr 100% (46) And enter these corrected data into Table 5, recalculating all the geometric parameters and velocities. After that, the width of the roll at the exit to the horizontal rolls is calculated. Before starting rolling on the mill, it is necessary to determine the hot dimensions of the thickness of the width of the slabs by their nominal dimensions in the cold state, taking into account the temperature of the metal t before entering the rolls: H G = H x (1 + 1.4 10 t) (47) B G = B x (1 + 1.4 10 t) (48) Rolling power: N B = 9.81 10 M about V B / R B kW (49) The size of the vertical rolls opening is determined by the known dependence: S j = B j -P / M mm (50) where M = 250 t / mm is the stiffness modulus of the vertical stands. The rolling speed in vertical rolls of universal stands is determined from the continuous rolling constant: V B H = V G h = const, whence V B = V G h / H m / s (51) For the most commonly used sheet steel grades according to the method of L.V. Andreyuk, the values of the coefficients given in Table 4 were obtained. Table 5 - Coefficients for calculating the true resistance of steel during hot rolling
Steel grades σ, kgf / mm After the final calculation of the width and energy-power parameters of rolling, the obtained data are entered into the general table of the rolling mode with horizontal rolls of roughing stands. Table 6 - Design mode for rolling 2.0 mm strips from 32 mm rolled stock.
Stand numbers Here, the parameters H, h, Δh should best be rounded to an accuracy of O, 1 mm. The program must also provide for manually set reductions along the stands, the finishing group of the mill, which is especially required when working without one or two stands. When calculating the speed of rolling in the stands of the continuous finishing group of the mill, we use the condition for the constancy of the second volume of metal: h 7 V 7 = ...... h 13 V 13 = const The filling and maximum rolling speed of the strip in the last stand No. 13, in order to obtain the required temperatures of the end of rolling and eliminate the temperature wedge along the length of the finished strips, can be taken according to approximate data, table 6 Table 7 - Rolling speeds in stand No. 13 depending on the thickness
For finished strip thickness, mm Calculation of the reduction modes in the finishing stands To calculate the reduction modes in the finishing stands (out of 7 stands, the finishing scale breaker of this design does not compress, tackle), we determine the thickness of the strip at the exit from each stand h i according to the formula of the Japanese scientist Iman Ihiro: h j = h 0 h k / (52) where h 0, h k h j - respectively, the initial, final and current thickness of the roll, mm. m = 0.3 + 0.21 / h k (53) In the interests of optimal loading of motors and rolls, exclusion of overloading of stands 7 and 8 and obtaining a good profile of the rolled strips, we assume the following distribution of the load over the stands: Received N Σ = 5.55 and the coefficients B j of loading on the stands will be: B 7 = 0.6 / 5.55 = 0.11; B 8 = 1.4 / 5.55 = 0.26; B 9 = 2.4 / 5.55 = 0.43; B 10 = 3.4 / 5.55 = 0.61; B 11 = 4.3 / 5.55 = 0.77; B 12 = 5.05 / 5.55 = 0.91. Table 8 - Values of coefficients а 0, a 1 а 2, а З, for С,, (designated, respectively, А 2, В 2, С 2)
A 2 - true heat capacity В 2 -density C 2 - thermal conductivity Empirical formulas for heat engineering coefficients for rolling temperatures 1250-800 ° С
A 2 - true heat capacity В 2 -density C 2 - thermal conductivity For temperatures 900 ° С-500 ° С when cooling the strips on the discharge roller table, ranges (900-725) ° С
A 2 - true heat capacity В 2 -density C 2 - thermal conductivity Note - rolling speeds for intermediate thicknesses not listed in the table can be determined as arithmetic mean values. Accelerations depending on the thickness of the finished strip can be taken as follows:
After the distribution of the reductions in the stands and the adoption of the tabular values of the rolling speeds, a check calculation is carried out for the load of the stands, the temperature of the end of rolling and the temperature wedge (t PC -t Зк). If these values require a change, then it is set by the corrected data and the calculation is performed again. The power parameters of rolling (P, N, M) and the temperature of the rolled bars and strips are determined for the front and rear ends. For the range of temperatures for cooling steel strips on the outlet roller table behind the finishing group of stands 900 ° - (650) 500 ° C for six groups of steel grades, the coefficients of empirical formulas were determined using a computer. Y = a O + a 1 (t j / 1000) + a 2 (t j / 1000) + a З (t j / 1000) (54) And a simplified form with a Z = 0 and a 2 = 0. 3. Organization of production Calculation of the production program of the mill 2500 The production program is the amount of products produced for a certain period (year, quarter, month), that is, it is a plan for the production of products. In rolling shops, the production program is calculated based on the average hourly productivity of the mill and the actual running time of the mill. Table 9 - Initial data for calculating the production program
Name, profile, dimensions Mill hourly productivity, t / h Specific gravity of the profile in the assortment, ()% 1.28ĥ1500 2.31500 3.3.9 ĥ1250 TOTAL We define the production program for the specified period of time. Table 4 - Production program of mill 2500 for July 2008
The name of indicators Units Indicators Time balance: Calendar time Nominal time Number of shifts per day Total work shifts Nominal time per shift Nominal time Current idle to nominal time Current downtime Actual time Performance: In fact. hour (A Wed) Per shift Per day Per month (quarter) 4. Economics of production Calculation of the economic efficiency of the introduction of a multi-roll coiler on the 2500 mill A new multi-roll underfloor coiler is being introduced instead of the old one. This increases the productivity to 706 t / h, the capacity of the old coiler was 646 t / h. The winding speed of the roll is increased up to 18 m / s, and the range of unwound products is also expanding. Table 11 - Technical and economic indicators of the mill
The name of indicators Unit of measurement Before implementation After implementation Average hourly productivity Annual fund of time Annual productivity List staff Metal consumption Cost of 1 ton of rolled metal Labor productivity Capital expenditures We determine the average hourly productivity for the "bottleneck" before and after the reconstruction (A cf1) and (A cf2), then the annual productivity of the mill. A G1 = A cf1 T f; (63) A G1 = 646.8 7080 = 4579344 t; A G2 = A cf2 T f; (64) A G2 = 706.8 7080 = 5004144 t. The annual increase in production will be ΔА Г2 = А Г2 -А Г1; (65) ΔА Г2 = 5004144-4579344 = 424800 t. We calculate capital investments: K = K 0 (1 + K T + K f + K M) P, (66) where K 0 is the initial cost of the machines; K T - coefficient taking into account transport and procurement costs (taken 0.05-0.08); K F - taking into account the construction of the foundation (taken 0.03-0.06); K M - taking into account the costs of equipment installation (taken 0.06-0.15); P is the number of units of this type of equipment. K = 25389000 (1 + 0.06 + 0.04 + 0.09) 4 = 120.8 million rubles. If additional equipment is installed, then additional costs are required for it: a) depreciation P a = K 0 N / 100, rub, (67) where K 0 is the initial cost of the car; H - depreciation rate for a given type of fixed assets,% R a = 120.8 12/100 = 14.4 million rubles. b) expenses for current repairs and maintenance of fixed assets P T = K 0 3.5 / 100; (68) P T = 120.8 3.5 / 100 = 4.2 million rubles. Then the running costs for additional equipment: P i = P a + P T; (69) P i = 14.4 + 4.2 = 18.2 million rubles. As a result of the implementation of the measure, the productivity of the mill increases, which means that we determine the annual savings on conditionally fixed costs: E i = P ΔA G, (70) where P - fixed costs in the cost of rolled products 1 ton, RUB / t; ΔА Г is the annual increase in the production of rolled products, i.e. Table 12 - Calculation of conditionally fixed costs per 1 ton of products
Name of cost items for redistribution Costs by item, rub. % of fixed costs by item The amount of fixed costs by item, rub. 1 Process fuel Energy costs: 2 El. energy 3 Technical water 5 Supporting materials 6 Basic salaries pr.work. 7 Additional salary 8 Contributions to social insurance 9 Replacement equipment including rolls 10 Maintenance 11 Depreciation of fixed assets 12 Work of transport shops 13 Other workshop costs 14 General plant costs E i = 169.7 424800 = 72.1 million rubles. We find the total savings from the implementation of the event: E total = E i -P i, (71) where E i is made up of individual savings obtained due to various factors; P i - additional costs that may arise. E total = 72.1-18.2 = 53.9 million rubles. We determine how the cost of 1 ton will change after the implementation of the event: C 2 = (C 1 A G1 E total) / A G2, rub / t, (72) where С 1 and С 2 is the cost of 1 ton of rolled products before and after implementation, rubles; A G1 and A G2 - annual production volume before and after implementation, t; E total - the total annual savings from the implementation of the event, rubles; Table 13 - Calculation of the cost of 1 ton of rolled products
Name of articles One ton Quantity 1 Semi-finished products 2 Waste: ends and trimmings scale waste Waste total Waste total set for / - / waste Σ0.036 0.01 0.027 0.073 1.000 3100 220 x x x 111.6 2.2 x 113.8 4336.4 3 Costs for redistribution and ORM Production cost С 2 = (9154.5 4579344-53.9) / 5004144 = 8377.37 rubles / t. Since the event requires capital costs, we determine: a) annual economic effect: E f = E total -E H K, rub, (73) where E H is the standard coefficient of the efficiency of capital investments, equal to 0.16. E f = 53.9-0.16 120.8 = 34.6. b) economic efficiency of capital investments: E = E total / K; (74) E = 53.9 / 120.8 = 0.44. E is compared with E N and a conclusion is made about the effectiveness of the measure. In our case, E> E H, then the implemented measure is cost-effective. c) payback period: T = K / E total, years; (75) T = 120.8 / 53.9 = 2.24 years. 5. Labor protection 5.1 Analysis of industrial hazards and measures to reduce them
The main hazardous, harmful production factors affecting workers of the 2500 hot rolling mill are: Heat radiation - leads to overheating of the body. To prevent overheating, you should wear the normal work clothes, consume a sufficient amount of liquid, salted soda water, tea, water from drinking fountains during the shift. When the first signs of overheating appear: nausea, dizziness, weakness, palpitations, the employee must leave the zone of high temperatures, take a cool shower, if the state of health does not allow him to return to work, it is necessary to contact the health center, notify the foreman or foreman about it. Industrial noise is a harmful factor. The noise exceeds the permissible limits if speech cannot be heard at a distance of 1 meter from the speaker. To reduce noise, personal protective equipment is used: antiphones, earplugs, helmets, headphones. Dust is a harmful production factor. When dust gets into the eyes, it injures the mucous membrane, causing conjunctivitis, which leads to visual impairment. If dust gets into your eyes, you should remove it yourself, you should immediately contact a health center. To protect the eyes from dust, protective glasses should be used, and dust masks should be used to protect the respiratory system. The personnel servicing the methodical furnaces of the 2500 mill (metal heaters, refractory workers) should remember that natural gas contains practically only hydrocarbons. The concentration of natural gas in the air in excess of 10% causes suffocation, because in this case, the oxygen content in the inhaled air will be 19%. The severity of carbon monoxide poisoning depends on the concentration of carbon monoxide in the inhaled air. If signs of poisoning appear, immediately remove people from this place, call gas rescuers, take an air analysis, find the place of the gas leak and eliminate it. .2 Safety instructions for the roller operator
The senior roller operator is responsible for the safe work practices of his team, for observing safety rules, therefore he is obliged to organize the work of each team member in strict accordance with the requirements of the technological instructions. While working in the mill, officials must: during routine inspections, repairs and transshipment of the mill stands, comply with the requirements of the regulation on the tag system. know all the dangerous places in the serviced section of the mill. check the absence of people in hazardous areas and objects on the mechanisms. check the presence and reliability of all fences and protective devices in the mill area. coordinate their actions in work and warn each other about the noticed danger. do not clutter the workplace, keep it clean monitor the serviceability of the tiled flooring, avoiding oily places on pedestrian paths, pedestrian bridges. be attentive to sound and light signals. give commands clearly, using the signals received in the shop. Inspect the surface of the rolls when the rolls of the stand are stopped, the guiding table is retracted and the water is closed for cooling at a distance of 1 meter. Roll the rolls of the stand to be performed at the command of the production foreman at minimum speed. measure the roll only when the roller table is stopped. It must be remembered that: it is forbidden to produce rolling, stands of aluminum, nickel, stainless steel and other materials. it is forbidden to lay hot undershoots on the rolls of the transfer clutch, chain, rope; undershoots must be placed in a pocket on the intermediate roller table. it is forbidden to be on the drive side, to go under the working stands, spindles and other devices during the work of the mill. To cross the roller conveyor when the mill is in operation on a footbridge. Literature 1 Diamidov V.D., Litovchenko A.Yu. "Rolling production" - Moscow "Metallurgy" Zotov V.F. Rolling production - Moscow "Metallurgy 2000" Bakhtinov V.B. "Technology of rolling production" - Moscow "Metallurgy 1983" Kuprin M.I. "Foundations of rolling theory" 1978 - Moscow "Metallurgy" Gulidov I.N. "Equipment for rolling shops" 2004 - Moscow "Intermet Engineering" Technological instruction for hot rolling of strips on mill 2500 TI-101-P-GL4-71-2005
; (4)
=5,6%.
= 45.5mm. 
; (4)
;
;
mm.
mm.
mm;
mm.
mm.
mm.
; (8)
; (9)
= 9.3m / s.
= 80s -1.
(15)
;
(16)
=3,8.
m
; (22)
; (24)
; (25)
; (28)
;
m;
m;
m.
; (34)
;
(36)
= 132.5m;
The pickling section is designed to provide the rolling mill with a hot-rolled pickled strip for pickling in a hydrochloric acid solution.
The pickling section includes two continuous pickling units (NTA).
The composition of each NTA:
- Decoiler;
- Right car;
- Shears for cross-cutting;
- Butt-welding machine (CCM);
- Loop pit;
- Trainer cage;
- Pickling bath;
- Disc shears;
- Guillotine shears;
- Winder;
The rolls from the warehouse are fed to the receiving conveyor by means of an electric bridge crane, with the help of which they are transported to the tilter, where they are tilted to a horizontal position. From the tilter, the roll is transferred by the rotary device to the lifting platform with the trolley.
The platform with the trolley, moving, puts the roll on the unwinder drum. The strip is then fed into the straightening machine. After that, the strip straightened in the straightening machine along the roller table goes to the pulling rollers, which are fed to the guillotine shears for cutting the front and rear ends of the roll.
Welding of the two ends of the strip is performed by CCM. The strip welded on the CCM is fed into the loop hole by pulling rollers. It is allowed to throw no more than 800 meters of the strip into the loophole. From the loop pit, the strip is fed into the “quarto” tempering mill through the baffle rollers, the bending device and the tensioning device. The tempering is carried out in order to destroy the scale, to speed up the pickling process, and also to ensure the required strip profile.
Regenerated hydrochloric acid is used to remove scale from the surface of hot rolled strips. The pickling process is performed to remove scale from the surface of the hot rolled strip. The scale is removed chemically, according to the reactions (1, 2, 3):
FeO + 2HCl = FeCl 2 + H 2 O (1)
Fe 3 O 4 + 6 HCl + H 2 = 3 FeCl 2 + 4H 2 O (2)
Fe 2 O 3 + 4 HCl + H 2 = 2 FeCl 2 +3 H 2 O (3)
In this case, the strip sequentially passes through the technological part of the unit in the following order:
- four deep-type pickling sections with strip immersion in pickling solution;
- bath of jet washing, consisting of five stages;
- drying device with additional blowing of the strip edges with air from the pneumatic system. Strip washing after pickling is carried out in a five-stage, jet washing bath.
After pickling, rinsing and drying, the strip goes to the disc shears. Circular shears - non-driven, with rotary cutting heads with a bevel cutter are designed for trimming strip edges. The strip after the disc shears, passing the tensioning devices, enters the output guillotine shears. On guillotine shears, the strip is cut to obtain the optimal mass of pickled bales with cutting seams. The strip is wound alternately on two coilers.
Rental area
The rolling section has two continuous cold rolling mills: a four-stand "2500" mill and a two-stand reversing mill "1700".
Mill "2500" :
The 2500 four-stand mill is designed for rolling hot-rolled pickling stock in Quattro stands into cold-rolled strip of a given thickness. The coils are fed to a four-stand "2500" mill, where they are rolled with a reduction of up to 50 - 55% at a speed of up to 5 m / s.
The mill must perform the following tasks:
- stable rolling of strips at maximum productivity;
- obtaining rental that meets the requirements of standards and
technical conditions;
- minimal metal losses.
After NTA, the coils go to a lifting roller table with a pusher, designed to remove the roll from the receiving conveyor, lift it up to the decoiler axis and push (put it on) onto the decoiler drum.
The decoiler is designed for correct installation of the coil relative to the longitudinal axis of the mill, rotation of the coil to a position that allows gripping the outer end of the strip, its task in the feed rollers and creating tension between the decoiler and 1 stand during rolling.
The working stands of the mill are designed to carry out the process of cold rolling of strips, i.e. to hold the work and backup rolls in a certain position, the possibility of their movement in the vertical plane, the rotation of the rolls and the perception of the forces arising during rolling. All four working stands of the mill are of the same design and dimensions.
The coiler is designed to create tension on the strip between the fourth stand and the coiler drum and to wind the strip into a roll. The coiler consists of a drum with a drive, a folding support, a pressure roller for clamping the end of the strip.
Reversing mill "1700" :
The 1700 double-stand mill is designed for rolling hot-rolled pickling stock in Quattro stands into cold-rolled strip of a given thickness. Rolling is carried out from wider strips with a transition to narrower ones. The coils are fed to the 1700 double-stand mill, where they are rolled with a reduction of up to 20 - 50% at a speed of up to 12 m / s.
The rolls that came from the NTA are transported by a walking beam to the loading section, where, if necessary, the roll is turned 180 for the task. Then the roll is taken by the transport roll car, from which it is fed to the decoiler (4-segment with a gearbox and a folding support). There the roll is fixed, a pressure drive roller is lowered onto the outer turns of the roll and the roll is scrolled to a position convenient for bending the front end of the guide table.
After bending the front end of the roll, the drive for rotation of the unwinder drum and the pressure roller is switched on to transport the strip to a 3-roller correctly pulling machine, where the deformed sections are straightened and the necessary bending of the front end of the strip is ensured (the formation of a "ski") for subsequent transportation and its task into the gap of the work rolls of the 1st stand.
Stands: two working stands with guiding fittings, drives, mechanisms for handling work and back-up rolls, a system of axial displacement of work rolls are designed to carry out the process of cold rolling of strips.
A distinctive feature of this rolling mill is the use of hydraulic pressure devices (HPU). GNU are designed to regulate the position of the upper back-up rolls, ensure the required rolling force and compensate for the effect of reducing the diameter of the rolls. The hydraulic pressure devices are double-acting hydraulic cylinders. The main advantage of the GNU is its high performance relative to the pressure screws of the traditional (mechanical) type, the absence of a negative impact on the cage head.
The equipment presented above makes it possible to reduce the thickness difference of the rolled metal over the strip section, to increase the yield of suitable metal, and to reduce losses in the production process.
Coiler Designed for winding the strip into a roll, as it leaves the working stands during the second pass, as well as to maintain the strip tension.
Training mills "1700" and "2500" :
Also, the rolling department of the shop is equipped with two single-stand tempering mills "2500" and "1700". These mills are equipped with one tempering "quattro" stand and have no fundamental differences, with the exception of the maximum allowable width of the rolling strip.
Tempering is a finishing operation in the production of thin strips and sheets of steel and non-ferrous metals, consisting in their cold rolling with low reductions (usually no more than 3%). As a rule, the metal is tempered after heat treatment. As a result of tempering, the yield point increases, thereby reducing the possibility of shear lines forming on the metal during cold stamping, which spoil the surface of the products.
The rolls assigned for training are installed by an electric bridge crane using pliers on the loading conveyor, so that the axis of the roll coincides with the longitudinal axis of the conveyor. The rolls are transported by the loading conveyor to the tilter, tilted from vertical to horizontal position and placed on the cradle of the transfer carriage. Then the roll is fed to the unwinding rollers, where, with the help of guillotine shears, the front and rear ends of the roll are cut.
After removing the defective areas, the roll is wound by reverse rotation. The roll is then fed by the transfer car to the walking beam, which transports it to the decoiler drum.
Before the strip is put into the stand, the strip passes through the pull rollers. If necessary, lower the upper roller to facilitate the task of the strip into the work rolls of the rolling stand or to roll the jammed front end of the strip.
The tempering of cold-rolled annealed strip is carried out at a specified reduction rate for each steel grade. Adjustment of compression in the course of training is carried out by pressure screws, the profile of the strip is adjusted by a hydraulic anti-bending system.
When tempering metal, after capturing the strip and winding 5-10 turns on the reel drum, it is possible to turn on the wet tempering system. Through the collectors located on the inlet side of the stand, the tempering fluid is supplied to the "working shaft-strip" zone from above and below. Through the collectors located on the output side of the stand only from the bottom, the tempering fluid is supplied to the zone "working shaft - support shaft". After the tempering stand, the strip passes through a system for blowing off residual tempering fluid from the surface, which provides:
Complete removal of the remaining tempering fluid in the area between the upper support and upper work rolls using air nozzles;
Complete removal of the remaining tempering fluid from both sides of the strip using air nozzles located on the upper and lower rods, and from the edges of the lower side of the strip using groups of extreme air nozzles;
Transfer of the remaining training fluid to the collection tank.
When approaching the rear end of the strip on the unwinder, the supply of the temper fluid stops.
After the tempering stand, the strip goes to the coiler. Which is intended for winding the strip into a roll, as it leaves the tempering stand, as well as to maintain the strip tension. Further, with the help of the roll removal cradle, the metal is sent for packaging.